Francisco de Orellana
For a long time, the Amazon River was named the "Rio de Orellana" after this lunatic. Despite huge natural obstacles, Orellano became the first known person to chart the entire famous river, riding the water all to the mouth where he proceeded to sail back to Spain. When he returned, he became single-handedly responsible for the great "El Dorado" myth, telling everyone the river was banked by golden cities and women-run societies like those of the Amazons of Greek mythology (ironically, it was his own myth-making that led to the river's modern name). Orellana returned to the river in his later life, but the second trip was a disaster: dozens of his men died, and Orellana himself drowned in his namesake river. His quixotic life has inspired many fictional tales, including Werner Herzog's acclaimed film Aguirre: The Wrath of God, which you must watch if you are interested in observing an entire spectrum of crazy people.