Prince Henry, for all these reasons, made Sagres a center for cartography, for navigation, and for shipbuilding. He knew that the unknown could be discovered only by clearly marking the boundaries of the known. This meant, of course, junking the caricatures drawn by Christian geographers and replacing them with cautious, piecemeal maps. And this required an incremental approach.

In the spirit of the portolanos, the coast pilots, he accumulated the bits of many mariner’s experiences to fill out an unknown coast. The Jews, wherever they were, had long since become powerful cultural ambassadors and cosmopolitanizers. The Catalan Jew from Majorca, Jehuda Cresques, son of the cartographer Abraham Cesques, whom we have already met, was brought to Sagres, where he supervised the piecing together of the geographic facts brought back by Prince Henry’s seafaring explorers. […]

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