According to Polhem's autobiography, the event that marked the beginning of his career was the successful repair of the unfinished medieval (16th century) astronomical clock by Petrus Astronomus at Uppsala Cathedral, which had remained unfinished and broken for more than a century.
He first appears by name as a lecturer in astronomy at Uppsala University, where between 1508 and 1509 he conducted a series of lectures.
Petrus Camper | Petrus Plancius | Petrus | Petrus Ramus | Petrus Christus | Lars Petrus | Jacques Fred Petrus | Petrus Van der Velden | Petrus Hofstede de Groot | Petrus de Natalibus | Petrus Codde | Petrus Canisius van Lierde | Petrus Astronomus | Petrus Alphonsi | Petrus Alfonsi's Tetragrammaton | Joseph Petrus Hendrik Crowe |