Who wrote a book on geography? Euclid

Eratosthenes

Archimedes

Pythagoras

It was Eratosthenes wrote a book on geography

Several astronomers and mathematicians before and after Eratosthenes tried to accurately measure the circumference of the Earth, but it was Eratosthenes that came through. He found the circumference of the Earth.

Eratosthenes also contributed to geographic source of the river.