Sphere of Sacrobosco

Johannes de Sacrobosco’s "Sphere" ("De sphaera mundi") is a foundational medieval introduction to astronomy and cosmology, widely used in universities from the thirteenth century onward. Though not a horoscope manual, it is significant for astrology because it explains the structure of the heavens, the motions of celestial bodies, and the basic astronomical framework on which astrological interpretation depended; readers will find concise expositions of the earth’s shape, the celestial spheres, and the movement of the stars and planets.

Johannes de Sacrobosco was a medieval scholar whose influential astronomical treatises, especially the 'De sphaera mundi,' were foundational for later cosmological and astrological learning. While not an occult author in a strict sense, his works were widely used in the intellectual background of medieval and Renaissance esoteric traditions.