Prester John

Portuguese maritime explorers had been gradually probing southwards along the west coast of Africa since the early part of the 15th century, seeding spores of the Portuguese language, religion, and trade interests at numerous points along the way. These journeys were both enterprises in their own right, insofar as trade off the African coast was an end unto itself, as well as an effort to establish Portuguese primacy in the spice trade with India through the discovery of a viable sea route to the east. There was also something of a quasi-religious objective to the undertaking: locating the mythical Kingdom of Prester John, a fabled Christian empire thought to exist somewhere in Africa.

By the 12th century, it was believed that far to the east, beyond the lands controlled by the Muslim armies, lived a powerful Christian king named Prester John in the land of India. His kingdom was believed to be grand and contained many wonders. Marco Polo looked for Prester John, and the Crusaders wanted to reach out to Prester John. Portugal's Henry the Navigator sent his ships out with explicit instructions of what they should do if they met Prester John, and on his historic voyages, Columbus carried two books, The Travels of Marco Polo and The Travels of Sir John Mandeville, both of which have long passages on Prester John.