However, there is little or no evidence that anyone ever believed that the world is flat, and no evidence that educated people ever did so. [Jeffrey Burton Russell]?, an American scholar whose main contribution to historical scholarship is a series of books on the history of concepts of evil and ideas of Satan, explored the issue in his Inventing the Flat Earth: Columbus and Modern Historians. Russell discovered that a series of 19th century popular historians and serious historians invented and perpetuated this legend in the face of overwhelming evidence to the contrary.
Russell, Inventing the Flat Earth (ISBN 027595904X (amazon.com, search)).