Nordestear y noruestear — the compass variation in the carrera de Indias

By 1590 the fact that a magnetic needle does not point true north everywhere had a Spanish sailors' vocabulary — nordestear, noruestear — a rule about where the error vanished, and a printed warning that a navigator ignoring it will make landfall somewhere other than intended. The book recording all three is a Jesuit natural history: it adds that no philosopher or cosmographer could explain the effect, that the pilots knew it anyway, and that the informant was Portuguese.