Ptolemy, Alexandrian Greek astronomer and geographer, 1508. Ptolemy (Claudius of Ptolemaeus) (c100-c170 AD), using a quadrant to observe the Moon and stars. Urania, Muse of Astronomy, instructs him. An armillary sphere can be seen in the bottom left corner of the image. Ptolemy is shown wearing a crown as he is often confused with the Ptolemaic kings of Egypt. From Margarita Philosophica by Gregor Reisch. (Basel, 1508).