inventio fortunata (also inventio fortunate, inventio fortunat or inventio fortunatae), ""fortunate, or fortune-making, discovery"", is a lost book, probably dating from the 14th century, containing a description of the north pole as a magnetic island (the rupes nigra) surrounded by a giant whirlpool and four continents. no direct extracts from the document have been discovered, but its influence on the western idea of the geography of the arctic region persisted for several centuries.