While Thales was in Egypt, he was supposedly able to determine the height of a pyramid by measuring the length of its shadow when the length of his own shadow was equal to his height. Thales learned about the Egyptian rope-pullers and their methods of surveying land for the Pharaoh using stakes and ropes. Property boundaries had to be re-established each year after the Nile flooded. After Thales returned to Greece about 585 BC with notes about what he had learned, and Greek mathematicians translated the rope-and-stake methods of the rope pullers into a system of points, lines and arcs. They also took geometry from the fields to the page by employing two drawing tools, the straightedge for straight lines and the compass for arcs. (SeeConstructions with compass and straightedge). The Greeks named their paper explorations "geometry" for "earth measure," in honor of the Egyptians from whom the knowledge came.