Today Eratosthenes' method [of calculating the circumference of the earth] seems almost banal … yet it is inaccessible to prescientific civilizations, and in all of Antiquity not a single Latin author succeeded in stating it coherently.

3.2, "Geodesy and Mathematical Geography", p. 68 - The Forgotten Revolution: How Science Was Born in 300 BC and Why It Had to Be Reborn (2004)