Bolesław I the Brave in 1025 he had himself crowned King of Poland. He was the first Polish ruler to receive the title of "rex" (Latin: "king"). He was an able administrator who established the "Prince's Law" and built many forts, churches, monasteries and bridges. He introduced the first Polish monetary unit, the "grzywna", divided into 240 "denarii", and minted his own coinage. Bolesław I is widely considered one of Poland's most capable and accomplished Piast rulers. Bolesław was born in 966 or 967, the first child of Mieszko I of Poland and his wife, the Bohemian princess Dobrawa. His "Epitaph", which was written
Mieszko I of Poland socially connected primarily by tribal structures. It appears that the elders cooperating with the Duke first felt the need for super-tribal unity, as expansion allowed them to broaden their influence. Mieszko and his people were described around 966 by Abraham ben Jacob, a Sephardi Jewish traveller, who at that time visited the Prague court of Duke Boleslav I the Cruel. Abraham presented Mieszko I as one of the four Slavic "kings", reigning over a vast "northern" area, with a highly regarded and substantial military force at his disposal. More precise contemporary records regarding Mieszko were compiled by Widukind of Corvey,