Volta do mar (the return by sea)

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The single most consequential piece of seamanship of the period, and the one least often named. Sailing south along the African coast is easy; sailing back north against the Canary current and the north-east trades is close to impossible for a square-rigged or lateen vessel that cannot point high into the wind. Portuguese navigators learned instead to leave the coast entirely on the homeward leg, standing far out into the open Atlantic on a north-westerly board until they reached the latitude of the westerlies, and only then turning east for Lisbon. The technique generalised. On the India run it became the volta do mar largo, a vast westward arc across the South Atlantic that took ships within sight of Brazil before the southern westerlies carried them east to the Cape — which is why Cabral reached the Brazilian coast in 1500 while sailing to India. The counter-intuitive core of it is that the fastest way home is to sail away from home first, and it required trusting a calculation over the evidence of the coastline.