Claudius Ptolemy (AD c100-170), Greek-Egyptian astronomer, geographer and mathematician at his observatory in Alexandria, Egypt. Among the instruments seen here are Ptolemy's rulers (lower center) and a copper disc (far right), which he used to demonstrate the law of reflection. At this observatory Ptolemy made the observations that supported Earth-center models of solar and planetary motion. This view dominated astronomical thinking until the mid 16th century. Engraving from Vies des Savants Illustres (1877).