De sermonum proprietate sive Opus de universo.

Also known as De rerum naturis. This dictionary or encyclopedia is the earliest known printed book to include a section dealing with medicine, and this brief section, Book 18, Chap. V concerning medicine and diseases, and other sections in the work on animals, plants, and minerals may be the first, or among the very first, printed texts on scientific subjects. Maurus's compilation may be considered either a dictionary or encyclopedia; it was the first of all printed encyclopedias. The book was printed by Rusch, the “R” printer. Authorities have dated the book before July 20, 1467 because  the first roman type used was thought to be the earliest Roman type ever cast. For an interesting paper on the book, including a translation of the chapter dealing with medicine, see E. C. Jessup, Ann. med. Hist., 1934, n.s., 6, 35-41. More recently it has been suggested that the book might have been printed between 1473 and 1475. ISTC No. ir00001000. For more details see the entry at HistoryofInformation.com at this link. Translated into English by Patricia Throop as Hrabanus Maurus, De universo: The Peculiar properties of words and their mystical significance, 2 vols. (Charlotte VT, 2009).