Cleomedes

Cleomedes was a Greek astronomer known for his handbook on the heavens, usually titled "On the Circular Motions of the Celestial Bodies." Drawing heavily on Stoic physics and the work of Posidonius, the treatise is a valuable introduction to elementary astronomy and preserves the famous accounts of how Eratosthenes and Posidonius measured the circumference of the Earth. His exact dates are unknown and much disputed by scholars, with estimates ranging widely from the first century BCE to the fourth century CE; he is most often placed in the early Roman imperial period.