The Renaissance Florentine navigator Amerigo Vespucci, who explored the coast of America from Florida to the tip of South America, was the first to declare South America a continent rather than a series of islands, as was previously thought. Vespucci also measured the earth's circumference more accurately than anyone before him and devised a system for determining exact longitude. Born into a noble family in Florence, Italy, Vespucci had an early interest in geography and navigation. He trained for a career in business, however, and was sent to Spain in 1492 as a representative of Florence's Medici family. While in Spain, Vespucci may have helped secure financing for the voyages of Christopher Columbus. His contact with Columbus and other explorers increased his interest in navigation, and he sought to make his own voyages of exploration. Vespucci made two voyages to the West, the first in 1499--1500 for Spain and the second in 1501--1502 for Portugal. During these expeditions, he explored over 6,000 miles of coastline and determined that the lands Columbus discovered were not islands off the continent of Asia but were part of a "new world." Using his unique system of celestial navigation, Vespucci also correctly theorized that two oceans, rather than one, lay between the west coast of Europe and the east coast of Asia. A letter allegedly written by Vespucci in 1504 claimed that he had made four voyages rather than two. However, this matter has been widely disputed, and no positive proof has been found to either prove or disprove the claim. In 1507 the German geographer Martin Waldseemuller published Vespucci's accounts of his voyages and suggested that the new lands to the West be named America in honor of the man who determined that they were new continents.