The Planisphere of Ptolemy, plate 1 from Harmonia Macrocosmica

Ptolemy's towering treatise the Almagest, dating from about 150 a.d., was the authoritative textbook on astronomy for nearly 1, 500 years. Arabic scholars and then mediaeval monks copied the Latin text in illuminated manuscripts before the age of print. Here the cartographer Andreas Cellarius described Ptolemy's geocentric conception of the universe. In the lower margins, the artist included imagined portraits of Ptolemy (lower right), and Aristotle (lower left), the chief source of Ptolemy's ideas.