jumping from a tower in Venice cannot be substantiated; since he was around 65 years old at the time.

Mariner's astrolabeThe earliest recorded uses of the astrolabe for navigational purposes are by the Portuguese explorers Diogo de Azambuja (1481), Bartholomew Diaz (1487/88) and Vasco da Gama (1497-98) during their sea voyages around Africa.