On spotting an island in the Carribean, (Santo Domingo was it?) Christopher Columbus, the story goes, thought that it was India and that he had successfully found a westward route to the land of spices, etc.
How coluld this be? Eratosthenes had measured the circumference of the earth to be 25,000 miles almost two millenia earlier. Was this just wishful thinking on Chris's part? Or was it that the absence of accurate clocks or watches aboard the Nina, Pinta, and Santa Maria made finding the longititude so difficult that Columbus really did not know where he was?