One of the world's earliest printed documents, Christopher Columbus's account of his first voyage to discover the New World, will come up for sale in London this month with a price tag of £500,000.The Columbus Letter, or Epistola Christofori Colom, is the explorer's remarkably humane description of his first encounters with the natives of Hispaniola and other Caribbean islands early in 1493. For sale: The Columbus Letter He wrote it on his return voyage to Spain for his sponsors, Ferdinand and Isabella of Aragon and Castile, and it was rushed into print so that the news could be...