Ptolemy (c.90-c.168), astronomer who lived in the Greek culture of Roman Egypt. Ptolemy is one of the most famous astronomers of antiquity. The Ptolemaic system in his Almagest documented previous Greek thought, and dominated Western science for over a thousand years. This artwork shows Ptolemy holding up a quadrant to measure the angle of elevation of the Moon. Behind him, the muse Astronomia is pointing towards the Moon. An armillary sphere, used to show the motion of the stars around the Earth, is at lower left. Although he is depicted here with a crown, Ptolemy is not thought to have been related to the earlier Ptolemies who ruled Egypt. Artwork from the 1508 edition of the German encyclopedia Margarita Philosophica by Gregor Reisch.