To Sagres came sailors, travelers, and savants from all over, each adding some new fragment of fact or some new avenue to facts. Besides Jews, there were Muslims and Arabs, Italians from Genoa and Venice, Germans and Scandinavians, and, as exploring advanced, tribesmen from the west coast of Africa. At Sagres, too, were manuscript records of the great travelers that Prince Henry’s brother Pedro had collected during his grand tour (1419-1428) of the European courts. In Venice Pedro had received a copy of Marco Polo’s travels along with a map “which had all the parts of the earth described, whereby Prince Henry was much furthered.”

With these facts came the latest navigating instruments and newest navigating techniques. The mariner’s compass was already well known, but its use was still haunted by superstitious fears of its occult power, believed to be akin to necromancy. Only a century before, tricks such as those performed with the lodestone had got Roger Bacon in trouble. At Sagres the compass, like other instruments, was tested only by whether it helped the mariner reach out farther and then find his way home. […]

“The Portuguese Discoverers”, from “The Discoverers”, Daniel J. Boorstin, The National Board for the Celebration of Portuguese Discoveries, Lisbon, 1987