Libellus de Medicinalibus Indorum Herbis (Cruz-Badiano codex, 1552)
A herbal of Nahua medicine finished at the Colegio de Santa Cruz de Tlatelolco on 22 July 1552, dictated in Nahuatl by the indigenous physician Martin de la Cruz and put into Latin by the indigenous Latinist Juan Badiano. It is the earliest book of medicinal plants of the native peoples of the Americas, painted by Nahua scribes, and it was made to raise money to keep the college that produced it open.
Why this wins its question: General accounts introduce this book as a charming Aztec herbal and stop at the picture of the plants. Everything that makes it consequential is in the parts they skip: two named indigenous authors who were teachers rather than informants, a medical system stated in its own categories of cold and hot and of tonalli, teyolia and ihiyotl, a fundraising motive that failed, a 1555 ban that gutted the college, an absence of ritual that the authors had reason to arrange, and remedies that entered European pharmacy without a name attached. This object binds each of those to peer-reviewed work, keeps the live dispute over the origin of the hot-cold system on the record, and marks the one priority claim in its sources as the retrospective reading it is.
Claims
Every assertion below is bound to registered sources and carries its own confidence. Weight them; do not treat the page as uniformly authoritative.
The Libellus was completed on 22 July 1552 at the Colegio de Santa Cruz de Tlatelolco. Martin de la Cruz, a Nahua physician, supplied and dictated the matter in Nahuatl; Juan Badiano, a Nahua reader in Latin at the same college, translated it. Both men were indigenous, and both were teachers there rather than pupils.
The manuscript is a small book, about 15 by 20 centimetres on Italian paper, of 140 pages hand-painted by tlacuiloque, the Nahua painter-scribes. It treats the uses of 227 plants, of which 185 carry an illustration and 64 are named without one.
It is ordered by ailment from the head downwards to the feet rather than by the characteristics of the plants, and it ranges from cataract and glandular tumours to hair loss and foul-smelling armpits - a working clinical arrangement rather than a botanical one.
The medicine it records is Nahua on its own terms, not European medicine with local plants substituted in. Illness is an imbalance of cold and hot, and health requires balance among three animating forces - tonalli in the head, teyolia in the heart, ihiyotl in the liver - each tied to a part of the wider world. Where Latin had no word, the Nahuatl term was left standing.
It is described in the literature as the first book of medicinal plants of the indigenous peoples of the American continent. The qualifier matters - it is a manuscript rather than an imprint, and earlier and parallel bodies of Mesoamerican plant knowledge existed that were never written in this form.
The book had a purpose beyond medicine. It was assembled as a fundraising gift for Charles V, meant to demonstrate the worth of the Colegio de Santa Cruz and prevent its closure. The attempt failed, and from 1555 indigenous men were barred from ordination to the priesthood, which removed the college's stated reason for existing.
What the codex leaves out is part of the evidence. Ritual and appeals to supernatural help not directed at the Christian God are absent, and the two authors were recent converts with an interest in concealing or suppressing them; the compendium form itself is taken from European herbaria. The surviving text is therefore a filtered record, and its filters are known.
Whether the hot-cold framework is Mesoamerican or imported is an open scholarly question. George Foster argued it is a simplified folk variant of Greco-Persian humoral pathology carried to Latin America; De Smedt and De Cruz prefer a Mesoamerican origin, citing the polarity of opposites in the wider cosmovision and the early date of this very codex.
Remedies from the Cruz-Badiano codex and from other early Mesoamerican sources passed into Spanish pharmacopoeia, and the indigenous contribution went largely unacknowledged then and later - a pattern that continues in the modern failure to credit indigenous communities in patents.
The manuscript left New Spain and did not come back for four centuries. It reached the royal library, passed to Cardinal Francesco Barberini - hence its other name, Codex Barberini - and entered the Vatican Library in 1902, where Charles Upson Clark located it in 1929. John Paul II handed it back in 1990, and it is now in Mexico's National Library of Anthropology and History.
Lacy-Niebla reads one entry as describing the principal symptoms of angina pectoris two hundred years before William Heberden. This is a retrospective diagnosis offered by a cardiologist in a cardiology journal, resting on the identification of a sixteenth-century description with a modern category, and it is recorded here as that author's reading rather than as an established priority.