(…) the equal sign (…) to be invented in 1557 by Robert Recorde of Oxford and Cambridge, who, inspired by geometry, remarked that no things could be more nearly alike than parallel lines and hence decided that such lines should denote equality.
Mlodinow, Leonard. The Drunkard’s Walk: How Randomness Rules Our Lives. New York: vintage Books, 2008. (via carvalhais)