First knowledge of a round not a flat earth

In follow up to our on air conversation about the initial understanding of the earth as a sphere, I copied this from the link regarding obelisks and angles.

http://www.zum.de/whkmla/period/disc/flatearth.html

Actually, Eratosthenes of Cyrene, head of the Great Library of Alexandria had proven the earth to be round. Knowing that on a certain day, at noon, an obelisk in Luxor (s. Egypt) would cast no shadow, at exactly the same time he measured the shadow of an obelisk in Alexandria. He knew the height of the obelisk and the distance between Alexandria and Luxor; the rest is trigonometry. Claudius Ptolemy's geography is also based on the concept of the earth being round, and sun, moon and the stars circling around the earth.

So, Ptolemy produced a map of a globular Earth as early as AD 140

http://www.timelinescience.org/resource/students/flat/flat.htm

it was not until much later of course that magellan sailed around it