Sacrobosco, Italy, fourteenth century

In addition to a study of the fundamentals of arithmetic, this manuscript of work by the astronomer Sacrobosco (d. 1256) is accompanied by the text for which he is best known, his treatise on the heavenly spheres. On the right-hand page here exhibited, the nine spheres are illustrated and described in order: the moving heavens, the stationary heavens, Saturn, Jove (Jupiter), Mars, the Sun, Venus, Mercury, and the Moon. In this celestial scheme, the Earth is at the center of the universe. A note on the left-hand page (between the two paragraphs) records that the manuscript was used by a Franciscan monk named Peter of the Order of St. John in 1399.

Parchment, 81 folios, 180 x 134 (125 x 80) mm, 1 column, 25 lines, in Latin, written in early Gothic script.