Jan Boner

A wealthy merchant and tradesman dealing with spices, metals, timbers, livestock, etc., he opened branch offices of his firm in many towns of Poland, Germany, Russia and Hungary.

As the king's banker and main purveyor to the royal court, Boner became one of the wealthiest men in Europe of his times.

[1] Among other deeds, he was able to recover the royal treasury from the verge of bankruptcy, having strengthened it with roughly 200,000 Red złoty, an incredible sum for 15th century standards.

He bought off the Royal properties for debts, among them the entire area of Spisz (for 12,000 Red złoty from Jordan of Zakliczyn), the town of Oświęcim and Ruthenian salt mines (for 14,000 Red złoty from Stanisław Kościelski) and a number of royal towns (including Sieradz, Gostynin, Radom, Sochaczew, Piotrków, Drohobycz, Rabsztyn, Głuchów, Tuchola, Nowy Sącz, Inowrocław and others).

In 1515, he became the manager of the Wieliczka salt mine, one of the most profitable enterprises of the epoch, from which a large part of the Poland's income was drawn.