The Codex Borgia or Codex Yoalli Ehēcatl is a Mesoamerican ritual and divinatory manuscript. It is generally believed to have been written before the Spanish conquest of Mexico, somewhere within what is now southern or western Puebla. The Codex Borgia is a member of, and gives its name to, the Borgia Group of manuscripts.
The codex is made of animal skins folded into 39 sheets. Each sheet is a square 27 cm by 27 cm (11x11 inches), for a total length of nearly 11 meters (35 feet). All but the end sheets are painted on both sides, providing 76 pages. The codex is read from right to left. Pages 29–46 are oriented perpendicular to the rest of the codex. The top of this section is the right side of page 29, and the scenes are read from top to bottom. So the reader must rotate the manuscript 90 degrees in order to view the codex correctly. The Codex Borgia is organized into a screen-fold. Single sheets of the hide are attached as a long strip and then folded back and forth. Images were painted on both sides and painted over with a white gesso. Stiffened leather are used as end pieces by gluing the first and last strips in order to create a cover. The edges of the pages are overlapped and glued together, making the sheet edges hardly visible under the white gesso finish. The gesso creates a stiff, smooth, white finished surface that preserves the images below.
The Codex Borgia features eighteen pages of an astronomical narrative that shows the yearlong alteration of the rainy and dry season.
The Codex Borgia was brought to Europe, likely Italy, some time in the early Spanish Colonial period. It was discovered in 1805 by Alexander von Humboldt among the effects of Cardinal Stefano Borgia. The Codex Borgia is presently housed in the Apostolic Library, the Vatican, and has been digitally scanned and made available to the public.
The first eight pages list the 260 day signs of the tonalpohualli (day sign), each trecena of 13 signs forming a horizontal row spanning two pages. Certain days are marked with a footprint symbol. Divinatory symbols are placed above and below the day signs.
Sections parallel to this are contained in the first eight pages of the Codex Cospi and the Codex Vaticanus B. However, while the Codex Borgia is read from right to left, these codices are read from left to right. Additionally, the Codex Cospi includes the Lords of the Night alongside the day signs.
Pages 9 to 13 are divided into four quarters. Each quarter contains one of the twenty day signs, its patron deity, and associated symbols.
Page 14 is divided into nine sections for each of the nine Lords of the Night. They are accompanied by a day sign and symbols indicating positive or negative associations.
Pages 15 to 17 depict deities associated with childbirth. Each of the twenty sections contains four day signs.
The bottom section of page 17 contains a large depiction of Tezcatlipoca, with day signs associated with different parts of his body.
Pages 29 through 46 of the codex constitute the longest section of the codex, and the most enigmatic. The pages refer to different veintena festivals. Together these images represent a 20-day period for the veintena cycle. The glyphs refer to dry and rainy seasons. They apparently show a journey but the complex iconography and the lack of any comparable document have led to a variety of interpretations ranging from an account of actual astronomical and historical events, to the passage of Quetzalcoatl —as a personification of Venus —through the underworld, to a "cosmic narrative of creation". Pages 37 and 38 depict Xolotl holding a Xiuhcoatl or "fire serpent" descending into the underworld with lightning. The sequence apparently ends with a New Fire ceremony, marking the end of one 52-year cycle, and the start of another.
Pages 47 through 56 show a variety of deities, sacrifices, and other complex iconography.
Pages 57 through 60 allowed the priest to determine the prospects for favorable and unfavorable marriages according to the numbers within the couple’s names.
Pages 61 through 70 are similar to the first section, showing various day signs winding around scenes of deities. Each of the 10 pages shows 26 day signs.
Page 71 depicts Tonatiuh, the sun god, receiving blood from a decapitated bird. Surrounding the scene are the thirteen Birds of the Day, corresponding to each of the thirteen days of a trecena. Page 72 depicts four deities with day signs connected to parts of their bodies. Each deity is surrounded by a serpent. Page 73 depicts the gods Mictlantecuhtli and Quetzalcoatl seated back to back, similar to page 56. They likewise have day signs attached to various parts of their bodies, and the entire scene is encircled by day signs.