The historian Cosmas of Prague recorded the legend of Oldřich and Božena, in his Chronica Boëmorum ("Chronicle of the Bohemians").

According to the legend, the young (and married) Oldřich set out on a hunt and travelled to Peruc.

[2] Oldřich abandoned his hunt and took Božena back to Prague, where she eventually gave birth to his illegitimate son Bretislaus.

[6] Božena's low birth is alluded to in the chronicle of Cosmas, which states that Oldřich first met her "riding through the village".

The illegitimate birth of her son Bretislaus to a low-born mother is believed to have made it necessary for him to resort to abduction when he later sought to marry a noble bride (Judith of Schweinfurt).