Materiality and the Limits of Internet Research: The “Borgia Map” and Its Facsimiles
/Challenging the received wisdom about the 1797 facsimile of a fifteenth-century mappamundi made from metal with enamel inlay proves not to be as easy as I had thought, and I hit the limits of the study of digital images. So, something of a cautionary tale.
One of the curious early maps that has long lurked at the edge of my historical awareness is the unique materiality of the early fifteenth-century mappamundi known as the Borgia map [n0]. Cardinal Stefano Borgia (1731-1804) acquired the work in 1794 for his museum in Velletri, just outside of Rome; Borgia left his collections to the Congregation di Propaganda Fide (he had been the congregation’s secretary and later prefect); the Museo Borgia was merged in 1902 with the Vatican Library.
The cardinal commissioned a facsimile of the map at his own expense (Heeren 1808, 256 n. ‘e’). Although the facsimile is often attributed to the cardinal himself, the work was overseen by his nephew, Camillo Camillo Giovanni Paolo Borgia (1777–1817), as recorded in the title (below). Modern commentators have presented the facsimile as the product of a unique, mechanical, but largely undefined reproduction process. Was it actually so?
A unique metal map?
The original map is unique because rather than being drawn in manuscript on paper or vellum, it was sculpted from metalwork in niello. This decorative technique has ancient roots: niello is a black enamel (nigellum in Latin) that is inlaid into an engraved or sculpted metal surface. The contrast of the niello with the polished surface, often silver but gold and other metals were also used, makes for a distinctive and attractive work:
Image of the Borgia Map scanned from a book, taken from wikipedia: https://en.wikipedia.org/wiki/Borgia_map#/media/File:Mapa_de_Borgia_XV.jpg
A detailed image of the original work is also available online from the Museo Galileo’s series of reproductions of large mappaemundi: go look at it; it’s a gorgeous work!
The map was made from copper in two halves, the join running vertically (north-south). The niello has become discolored in many parts and now appears as red and white pigments; the inconsistent pattern of variation indicates that the difference in colors is from discoloration (by age, presumably) and not an intentional element of the design. A number of nails or rivets were at some point driven through the plates, presumably to affix them to a surface, leaving holes.
I must offer one word of caution. In dating the creation of the work, scholars have necessarily dated its content to the early fifteenth century (starting with Heeren 1808, 260–62). However, there is no guarantee that the work itself was physically made then, nor that the work was intended as much as a statement of geographical knowledge as it was plainly a work of decoration. I do not think that the accomplished craftsman who made the Borgia map would also have been responsible for the image; who is to say what map, and when, the craftsman used as the basis of his metal work? I have no idea how one goes about dating such things, except that niello work was popular in the fifteenth and sixteenth centuries (Heeren 1808, 257). It is all a matter of considering the fashions and trends both in decorative display and in the treatment of early maps as suitable for display, which is to say of studying the Borgia map as a work of decoration first and as a work of geographical knowledge second.
A uniquely “cast” facsimile?
The facsimile also appears to be unique because of the manner in which it is presumed to have been created, via some kind of “cast.” Here’s the facsimile from the impression in the Library of Congress:
Camillo Giovanni Paolo Borgia, Apographon descriptionis Orbis terrae, figuris et narratiunculis distinctae, manu Germanica opere nigelliari discolorio circa medium saec. XV ([Rome], 1797). Copper engraving ⌀ 64 cm, on sheet 76 × 69 cm. Courtesy of the Library of Congress, Geography and Map Division (G3200 1450 .A6 1797); online at www.loc.gov/resource/g3200.ct007015
The received wisdom is that the cardinal had some kind of cast made from the sculpted metalwork of the original, and that the cast was then somehow reproduced to make the facsimile. For example, a recent blog post about the facsimile by a librarian in the Geography and Map Division of the Library of Congress, stated, “Cardinal Borgia had facsimiles printed from a cast of the original map” (Smith 2024); a post-2022 account of the facsimile by an antiquarian map dealer made the same claim and stated that this information came from the facsimile’s title: “As the Latin text at the bottom of the [facsimile] explains, Borgia had a cast made of the metal original and printed examples from the plates made from the cast in 1797.”
The title—in what to me seems especially tortuous Latin—does not actually state this. Here’s a transcription:
Apographon descriptionis Orbis terrae, figuris et narratinunculis distinctae,
Manu Germanica opere nigelliari discolorio circa medium Saec. XV. Tabulae aeneae Musei Borgiani Velitris consignatae,
Quod Camillus Joh. Paulii F. Borgia, Cruce Hieros. ornatus, ab intimo cubiculo Electoris Bavarici, Patrui Cardinalis exempla imitatus,
summa fide, maximoque artificio expressum, recognitumque Eruditis spectandum proponit A. C. ⊂I⊃I⊃CCXCVII
and my translation (to the best of my limited abilities!):
Apograph [exact copy] of a map of the earth in discolored niello work, with distinct figures and short narratives in a German hand, from about the middle of the 15th Century, on copper plates preserved in the Borgian Museum of Velletri, which Camillo Borgia, of the order of the Cross of Jerusalem, puts forward for study by the Learned, reproduced from examples [tracings?] by his paternal uncle, the cardinal, in the private library of the Elector of Bavaria, with the greatest fidelity, utmost skill, and recollection Anno Christe 1797
The idea that the facsimile was produced by a cast would seem to suggest the creation of some kind of wrong-reading relief printing surface, which might then be printed in a letter press. However, several points about the facsimile indicate that it was printed from a copper plate in a high-pressure intaglio rolling press. Look carefully at the detail from the LC’s facsimile: the texture of the thick lines mimicking those of the original map, as in the ‘E’ of “Europa,” reveal how the thick lines were actually made by closely spaced engraved lines; when printed, the lines appear to blend together. This is a basic technique in copper engraving to achieve lines that would otherwise be too thick to restrain the ink properly within a rolling press.
A relief printing surface would permit the printing of the thick lines as thick lines and would not require them to be emulated by closely spaced thin lines. Moreover, the fine lettering of the facsimile’s title is plainly from a copper-plate engraving and not from a relief printing surface. Also, digital images of the facsimile plainly reveal the plate mark created when an engraved copper plate is run through a high-pressure intaglio rolling press and permanently deforms the paper. Hermann Wagner (1892, 352) specified the plate mark as being 70 × 65 cm in size. The plate mark is admittedly not very clear on the Library of Congress copy (above), but is on the image of the impression held by the University of Michigan’s Clark Map Library and others. That is, in line with contemporary practices of reproducing maps, an engraving was prepared via a tracing of the original work (Edney 2022).
Nordenskiöld and the Idea that a Cast Was Made of the Borgia Map
The idea that some kind of cast was used to make the facsimile seems to have originated with the famed map historian Adolf Erik Nordenskiöld. He had studied an impression of the facsimile that he described and reproduced (in a collotype reduction) in the Swedish journal Ymer (Nordenskiöld 1891). Although he wrote that he had “obtained” the impression (see below), the print would be sold in 1892 to Enriquetta Rylands by the Italian dealer and publisher Leo Olschki (my thanks for this information to Donna Sherman, the Rylands Library’s map curator). Assuming that he had briefly owned the item, I presume that Nordenskiöld had sought to ease some financial strain by selling off this seemingly choice item. (He was not necessarily good with his personal finances; notably, he would have to sell off his entire early map collection in 1899.)
With the impression lodged in Manchester (and later with the John Rylands Research Institute and Library when it was established), Nordenskiöld had an English translation of his essay published as a separate monograph (again with the collotype reduction). The map was closely trimmed to the map’s bounding circle, excising any title or other marginal information:
The Rylands impression. Image supplied by the John Rylands Research Institute and Library, University of Manchester. See https://luna.manchester.ac.uk/luna/servlet/detail/maps002~1~1~414766~155817
Nordenskiöld thought that the impression was unique and argued that it was a monotype produced by the artists who had crafted the original work, in the first half of the fifteenth century. His idea was that as the base plates were being engraved, the craftsmen would have taken some kind of impression to gauge what the work would look like once the niello had been inlaid into the engraved lines:
I obtained [the print] from Venice, where it was exposed for sale as an old German wood-engraving. A closer examination of the details of the print soon show, however, that one has here not to do with a wood-engraving, but with a very imperfect metal-engraving. For the sake of certainty I consulted upon this point with several wood-engravers and engravers on metal, who were all agreed that the map was not printed from a wood-engraving, although, on the other hand, they were not agreed as to the kind of copper-engraving which was here exhibited. This is clearly owing to the fact that the map is not a copper-engraving in the ordinary sense, but such an impression as gold smiths take of their artwork designed for enamelling or guilloche work, to be able to follow the progress of the work and to see how it would appear when finished. In the history of the art of copper engraving one recognizes many prints of this kind, which are highly prized by the collector. I have certainly not had access to any originals of such work, but by comparison with carefully executed facsimile copies, it seems to me evident that the map in question originated in this way, and that it is thus not a copy of a plate designed for printing. (Nordenskiöld 1893, 7)
However, this argument was almost immediately dispelled when Walther Ruge (1891, 396) found the original map in the Museo Borgia, along with several impressions of the facsimile, one of which he was given, and then when Hermann Wagner (1892) found several more impressions in Germany. The facsimile was therefore not an early fifteenth-century monotype that predates all known European printed maps. Unfortunately, Nordenskiöld’s monograph is often cited as the key information source in modern library catalog records, and his incorrect conclusions shade the records.
Two further points disprove both Nordenskiöld’s argument and the modern idea of a cast being used to make the facsimile. Because he had not seen the original map, Nordenskiöld assumed that it was all of a single piece of copper. Had his impression been created as some kind of monotype, then it would either have to have been in two parts or show the plate-join along its central, vertical axis. Furthermore, it would be difficult to take a cast from the finished work, with the niello inlay, because in niello work, the inlay fills the engraved lines almost completely.
This last point also obviates Wagner’s (1892, 352) thought that the image of the original map had been transferred to the copper plate for engraving “by producing a negative print directly from the plate rubbed with color, etc.” That is, a colored ink might have been applied to the original work and then impressed onto a polished copper plate; the engraver would then have engraved between the transferred colors. This process is similar to some of the carbon black photographic processes used in the later 1800s to transfer images to zinc plates for reproduction (Edney 2022), and Wagner’s use of “negative print” (Negativdruck) is perhaps revealing in this respect. But such a pseudo-photographic practice is not attested, to my knowledge, in the 1790s. Again, such a process requires a clear difference in relief between the metal surface and areas of inlay.
All told, ideas of some cast or relief impression taken from the original metalwork, before or after the niello inlay, are grounded on the misapprehension of the physical nature of the original work.
A Failed Tangent: Were there Two Facsimiles?
Looking at the Rylands impression online, I noticed a significant difference between it and other copies of the facsimile, which seemed to plainly indicate that the Rylands impression had been printed from a different plate! The following image compares a small portion of the bottom edge of the map on the original (left), the Rylands impression (center), and the Library of Congress impression (right):
Note in particular how, on the Rylands impression, one diamond shape is blank and how waves fill the small space to the lower left of the diamond, differing significantly from the original and the LC impression. The LC impression also shows a circumferential line lacking in both the original and the Rylands impression. That is, there must have been two separate eighteenth-century facsimiles, maybe one commissioned by the cardinal, which would then raise the question of why the nephew would issue a second facsimile.
ALAS AND ALACK, when I studied the same portion of the Rylands impression not through the library’s website but in the high-res TIFF file that the library kindly sent me at my request—thanks!—I found that I was quite mistaken. The high-res image showed that the area of difference had been drawn by hand, in a different ink, in the process changing the look of the map. Indeed, further study of a multispectral image by the Rylands Advanced Imaging Team, which Donna Sherman also kindly sent me, indicated (a) there was a significant area of paper loss across the bottom of the Rylands impression that (b) was obscured by the mounting of the impression on a paper substrate. That is, in accordance with a common practice of conservators who seek to recreate the look of the original work, the area of loss had been carefully filled in (when? by whom?) by someone who had access to the complete facsimile so that they could reproduce each line:
Image supplied by the John Rylands Research Institute and Library, University of Manchester
However, the content of the diamond was in the area of loss and the conservator neglected to fill it in.
The differences between the impressions in areas without paper loss are minor, reflecting more the nature of the heavy abrasions that afflicted the Rylands impression. Not only was there paper loss, but the ink lying on top of the paper (a function of copper-plate engraving!) has been eroded. Bearing that in mind, the location of the lines, especially in terms of thicker shading, are the same.
After writing this up, I thought to see what Nordenskiöld might have said about the Borgia map and its facsimiles in his large study with facsimiles of early marine mapping, Periplus, and found this admission in which he distanced himself from his earlier argument:
As regards this map, I have to refer to my paper in Ymer, Stockholm 1891, pp. 83 et seq., and the above-quoted essay by W. Ruge [(1891)], pp. 396 et seq. The badly worn copy that I reproduced in Ymer was not supplied with any signature, and is supposed by connoisseurs to be a copper-engraving of the 15th century. Ruge, however, who has had access to Borgia’s own reproduction of the end of last century, has shown that it is identical with the impression copied in Ymer. (Nordenskiöld 1897, 84n2)
Indeed, in plate 39 of Periplus, Nordenskiöld reproduced not the abraded image from his 1891 and 1893 works, but rather Borgia’s facsimile, albeit trimmed to the map’s bounding circle.
Here, then, is a limit to online research. Sometimes, you just have to get in closer than what online resources might permit. Ultimately, I need to go see some actual impressions of these facsimiles, which I won’t be able to do until later this year. It is always best to consult works in the original … now, can I persuade someone to pay me to go to Rome to actually look at the Borgia map in all its niello glory? Would the curators allow me to run a finger over it to gauge the difference in relief between the surface and the inlay?
A Further Facsimile
The cardinal’s acquisition of the original metalwork map is discussed in two early sources. The Nuremberg antiquary Christof Gottlieb von Murr (1802, 26–28) transcribed two letters from the cardinal about the map, dating from December 1794 and January 1795. The transcriptions deal entirely with the map’s content, but the dating of the first letter indicates that the cardinal had acquired the map at some point in 1794.
In the primary contemporary source, Jean-Baptiste-Louis-George Seroux d’Agincourt (1730–1814) wrote about the “one that got away” in his six-volume history of art from fourth-century “decadence” to sixteenth-century “renewal.” (So, very much a stadial history of the shift from medieval ignorance etc. to Renaissance glory.) The Borgia map features in three places in this complex work, originally issued in fascicles with separate paginations; moreover, Seroux d’Agincourt completed only the first two volumes before his death, and the remainder were issued or assembled posthumously by editors. Seroux d’Agincourt provided his own reduced facsimile of the Borgia map, with a detail of part of Europe at the original size, as an example of sculptural process and “gothic” (blackletter) script:
“Mappamondo inciso sopra una lastra di rame, specie di lavoro alla damaschina,” in Seroux d’Agincourt (1810–23, 4: pl. Sculpture 40). Copper engraving, 40.5 × 30.5 cm. - sourced from https://searchworks.stanford.edu/view/xx799sr6117
and he reviewed the map and its curatorial context in two separate passages, in volume 2 (1810) and in volume 3 (1823). The relevant portion of the initial passage translates roughly as:
This plate presents the reduced image of a terrestrial world map, engraved on a circular copper plate, today deposited in the museum of Cardinal Borgia in Velletri (c). Compared with the celestial globe of which plate XXV offers a drawing, it can give an idea of what was, in a genre almost similar, but at a distance of two or three centuries, the state of the art among nations which, in other respects, present such marked differences. [n1]
Note (c) further explained:
(c) In 1794, an antiquarian who, in his travels, was occupied, I believe, as much with trade as with research into antiquities, showed me this world map, without showing me any intention of wanting to get rid of it, and he allowed me to have it drawn as I present it here. Sometime later, Cardinal Borgia, who spared nothing to enrich his museum, managed to obtain this interesting monument. His nephew had it engraved at full size. The [original] map is composed of two pieces of copper of equal size, and a line and a half thick, which are attached together, at intervals, by the heads of small nails. The large circular black spots, on the traced part of my plate, indicate holes made after the writing, since they sometimes cut it. The engraving is half a line deep. The black composition which fills the sizes appears to be niello as explained by Vasari and by Benvenuto Cellini, i.e., a mixture of silver, lead, copper, sulphur, and pitch. As there is no evidence that prints were made from this copper [metalwork], we can believe that it was furnished with niello at the time of its making, and that this must have been placed a little before the discovery of the art of making prints from copper engravings. (Seroux d’Agincourt 1810–23, 2:72; repeated by Santarém 1849–52, 3:248–49) [n2]
[Significantly, Nordenskiöld (1891, 1893) did not cite this portion of Seroux d’Agincourt’s comments, perhaps because it contradicted his argument that his facsimile impression had been printed as an artist’s proof before the niello was applied.]
In the second, posthumously published passage, Seroux d’Agincourt modified the narrative slightly. Having listed some more of the map’s annotations, he further noted:
In the notes accompanying the text, we can see several other examples of these legends; we can also consult, in this regard, the large plate that Cardinal Borgia, who after me became the owner of this curious monument, had engraved at the same size from a tracing taken from the original, a plate that his nephew Camillo Borgia published under this title: Apographon descriptionis orbis terræ figuris et narratiunculis distinctæ, manu Germanica, opere nigelliari discolorio, circà medium sœculi xv etc. summa fide maximoque artificio expressum recognitumque. 1797. It is worth noting that this plate was engraved several years after the one that I am presenting to the public today. (Seroux d’Agincourt 1810–23, 3:37, re sculpture pl. 40) [n3]
So, the cardinal acquired the map and had a tracing made, from which nephew Camillo had the engraving done.
I should also note that Seroux d’Agincourt’s account flatly contradicts the usual statement that Cardinal Borgia (or one of his agents) acquired the original map in Portugal in 1794. I have no idea of the origin of this oft-repeated idea, but in 1794 the cardinal was running Rome on behalf of Pius VI.
Seroux d’Agincourt’s facsimile was later copied and published in brown/sepia ink in 1884 in the ninth edition of the Encyclopaedia Britannica (vol. 10, pl. 2, for “Geography”).
Arnold Heeren
The cardinal sent a number of manuscript tracings and of impressions of the facsimile to scholars and learned academies around Europe. In particular, he sent an impression and a manuscript account of the map to Arnold Heeren (1760–1842), a professor of history at the University in Göttingen. Moved by the uniqueness and importance of the map, Heeren decided to give a lecture about the map, on 28 July 1804; when informed of this, as an honorary member of the Göttingen royal academy of sciences, the cardinal sent a larger packet of impressions of the facsimile (Heeren, 1808 #114426@256 n. ‘e’, 257 n. ‘g’). Drawing on the cardinal’s information, Heeren (1808, 260 n. ‘k’) also refuted the supposed origin of the Borgia map in Portugal, when he noted that it had “migrated through several cities of Italy until it reached the Museum of Velletri.”
Heeren did not record the full title of the facsimile but abbreviated it as “apographon monumenti geographici” (copy of [the] geographical monument) (Heeren 1808, 256). Nor did his essay suggest that it was actually accompanied by the facsimile, and there was no mention of the facsimile in either the volume index or any instructions to the binder. Nordenskiöld therefore argued that no image accompanied Heeren’s essay. However, Wagner (1892) found that some impressions of the facsimile had been tipped into some—but not all—copies of the academy’s published proceedings for 1804–8, following Heeren’s essay. Hathi Trust has usefully digitized the volume held by the University of Michigan, with the map bound in; the paper is trimmed past the plate mark along three sides (but it remains visible across the bottom, just below the title).
Notes
n0. The same label has, however, also been applied to other early maps in the cardinal’s collection! For Piero Falchetta (2006, 36–50), “the Borgia map” was Borgiano V (modern Vatican MS Borg.Carte.naut.V), not XVI. There’s also “the Borgia chart” is the Diego Ribeiro “planisphere” of 1529 (modern Vatican MS Borg.Carte.naut.III).
n1. “Cette planche présente l’image réduite d’une mappemonde terrestre, gravée sur une plaque de cuivre circulaire, aujourd’hui déposée dans le muséum du cardinal Borgia à Velletri (c). Rapprochée du globe céleste dont la planche XXV a offert un dessin, elle peut donner une idée de ce qu’était, dans un genre à-peu-pres pareil, mais à la distance de deux ou trois siècles, l’état de l’Art chez des nations qui, sous les autres rapports, présentent des différences si marquées.”
n2. “(c) Eu 1794, un antiquaire qui, dans ses voyages, s’occupait, à ce que je crois, autant de commerce que de recherches d’antiquité, me fit voir cette mappemonde, sans me témoigner l’intention de s’en défaire, et me permit de la faire dessiner telle que je la présente ici. Quelque tems après, le cardinal Borgia, qui n’épargnaît rien pour enrichir son muséum, parvint à se procurer ce monument intéressant. Son neveu l’a fait graver dans toute sa dimension. Il est composé de deux pièces de cuivre d’égale grandeur, et d’une ligne et demie d’épaisseur, qui sont attachées ensemble, de distance en distance, par des tètes de petits clous. Les grandes taches noires circulaires, sur la partie calquée de ma planche, indiquent des trous postérieurs à l’écriture, puisqu’ils la coupent quelquefois. La gravure a une demi-ligne de profondeur. La composition noire qui remplit les tailles parait étre le niello indiqué par Vasari et par Benvenuto Cellini, qui était un mélunge d’argent, de plomb, de cuivre, de soufre et de poix. Comme il n’y a point d’indice que l’on ait tiré des estampes de ce cuivre, on peut croire qu’il a été garni de niellure au moment de sa confection, et que celle-ci doit être placée un peu avant la découverte de l’art de tirer des empreintes des gravures sur cuivre.”
n3. “On peut voir, dans les notes qui accompagnent le texte, plusieurs autres exemples de ces légendes; on peut aussi consulter, à cet égard, la grande planche que le cardinal Borgia, devenu, après moi, possesseur de ce monument curieux, en a fait graver de la grandeur même, et d’après un calque pris sur l’original, planche que son neveu Camille Borgia a publiée sous ce titre: Apographon descriptionis orbis terra figuris et narratiunculis distincte, manu Germanica, opere nigelliari discolorio, circà medium sœculi xv etc. summa fide maximoque artificio expressum recognitumque. 1797. Il n’est pas inutile d’observer que cette planche n’a été gravée que plusieurs années après celle que je présente aujourd’hui au public.”
Works Cited
Edney, Matthew H. 2022. “The Copy: Printing Processes and the Reproduction of Early Maps, 1830–1945.” Portolan 113: 48–63.
Falchetta, Piero. 2006. Fra Mauro’s World Map with a Commentary and Translation of the Inscriptions. Trans. Jeremy Scott. Turnhout, Belgium: Brepols for the Biblioteca Nazionale Marciana, Venice, and the Università IUAV di Venezia-CIRCE.
Heeren, A. H. L. 1808. “Explicatio planiglobii, orbis terrarum faciem exhibentis, ante medium saeculum XV. Summa arte confecti; Musei Borgiani Velitris; agitantur simul de historia mapparum geographicarum recte instituenda consilia.” In Commentationes Societatis Regiae Scientiarum Gottingensis [vol. 16] ad a. MDCCCIV–VIII, commentationes historicae et philologicae, 250–84. Göttingen: Heinrich Dieterich.
Murr, Christophe-Theophile de. 1802. Histoire diplomatique du chevalier portugais Martin Behaim de Nuremberg, avec la description de son globe terrestre. Trans. Hendrik J. Jansen. 3rd ed. Strasbourg and Paris: Treuttel and Würtz. Originally published as Christoph Gottlieb von Murr, Diplomatische Geschichte des portugesischen berühmten Ritters Martin Behaims (Nuremberg: Johann Eberhard Zeh, 1778).
Nordenskiöld, Adolf Erik. 1891. “Om ett aftryck från XV:de seklet af den i metall graverade världskarta, som förvarats i kardinal Stephan Borgias Museum i Velletri.” Ymer 11: 83–92.
———. 1893. An Account of a Copy from the 15th Century of a Map of the World Engraved on Metal, which is Preserved in Cardinal Stephan Borgia’s Museum at Velletri; Copied from “Ymer,” 1891. Stockholm: A. L. Norman.
———. 1897. Periplus: An Essay on the Early History of Charts and Sailing Directions. Trans. Francis A. Bather. Stockholm: P. A. Norstedt.
Ruge, W. 1891. “Zur Geschichte der Kartographie.” Zeitschrift für wissenschaftliche geographie 8: 393–404.
Santarém, Manuel Francisco de Barros e Sousa, Visconde de. 1849–52. Essai sur l’histoire de la cosmographie et de la cartographie pendant le Moyen Age, et sur les progrès de la géographie après les grandes découvertes du XVe siècle, pour servir d’introduction et d’explication à l’Atlas composé de mappemondes et de portulans, et d’autres monuments géographiques, depuis le VIe siècle de notre ére jusqu’au XVIIe. 3 vols. Paris: Imprimerie Maulde et Renou.
Seroux d’Agincourt, Jean-Baptiste-Louis-George. 1810–23. Histoire de l’art par les monumens, depuis sa décadence au IVe siècle jusqu’à son renouvellement au XVIe. 6 vols. Paris: Treuttel et Würtz.
Smith, Cynthia. 2024. “Cardinal Borgia’s Unusual Map of the World.” Worlds Revealed: Geography & Maps at the Library of Congress. 3 October 2024. https://blogs.loc.gov/maps/2024/10/cardinal-borgias-unusual-map-of-the-world/.
Wagner, Hermann. 1892. “Die Kopien der Weltkarte des Museum Borgia (XV. Jahrh.).” Nachrichten von der Königl. Gesellschaft der Wissenschaften und der Georg-August-Universität zu Göttingen 1892, no. 10: 349–61.
