Eratosthenes

Eratosthenes of Cyrene (c. 276 BCE – c. 195/194 BCE) was a Greek mathematician, geographer, poet, astronomer, and music theorist. He was also the chief librarian at the Library of Alexandria.

At some point during his lifetime, Eratosthenes wrote a work on geometry, which calculated the distance between the Sun and Earth as being two hundred and fifty thousand stadia. He made the calculations after comparing the shadow angles of and Alexandria when the sun striked both cities on the summer solstice.

His work was later inscribed on papyruses in Egypt and was used for study by geographers in the Great Library.

Reference

 * Assassin's Creed: Origins