Inventio Fortunata is a lost book containing a description of the North Pole as a magnetic island (the Rupes Nigra), a 33-mile-wide black rock, surrounded by a giant whirlpool and four continents.

The book is said to be a travelogue written by a 14th-century Franciscan (Minorite) friar from Oxford who travelled the North Atlantic region in the early 1360s, making some half-a-dozen journeys conducting business on behalf of the King of England (Edward III). In the book he described what he found, on his first journey to the islands, beyond 54 degrees north, which he presented to the King.
Unfortunately, by the time Atlantic explorers were seeking information in the 1490s, the Inventio had gone missing...

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