A Holy Roman Emperor stood barefoot in the snow for three days to beg a pope's pardon

In 1077, Holy Roman Emperor Henry IV traveled to the Italian castle of Canossa and waited barefoot in the snow for three days to have Pope Gregory VII lift his excommunication. The two had clashed over who got to appoint bishops, a struggle known as the Investiture Controversy over whether emperors or popes held final authority in Christendom. Henry's humiliation became proverbial — 'going to Canossa' still means a humbling climbdown — though he resumed fighting Gregory within a few years.

— Wikipedia contributors, Investiture Controversy — January 1077