It is said that swimming has been known since prehistoric times. Drawings of swimming from the Stone Age were even found in "the cave of swimming" near Wadi Sora in southwestern Egypt. In 1538 Nicolas Wynman, German professor of languages, wrote "Colymbetes", the first swimming book. Competitive swimming started around 1800 in Europe, mostly using the breaststroke. Competitive swimming started in 1800 in Europe, using mostly breaststroke. John Arthur introduced the freestyle, then called the trudgen, in 1872, copying it from Native Americans. Competitive swimming took part in the first Olympic Games in 1896, which was hosted by Athens. Richard Cavill improved the trudgen in 1902 by using the flutter kick. The World Swimming Association was then formed in 1908. The Butterfly was a variant of breaststroke at first, until it was accepted as a separate style in 1952. Written references of swimming have been dated back to 2000 B.C. including Gilgamesh, the Iliad, the Odyssey, the Bible (Ezekiel 47:5, Acts 27:42, Isaiah 25:11), Beowulf, and other sagas, although the saga is never described. There are also many mentions of swimming in the Vatican, Borgian and Bourbon codices.