According to his biographer Einhard, Charlemagne was unhappy about his coronation, a fact that later historians have interpreted as displeasure about the Pope's assumption of the key role in the legitimation of Imperial rule. Instead of the traditional recognition by popular acclamation, Leo III had crowned Charlemagne at the outset of the ceremony, just before the crowd acclaimed him. In September 813, Charlemagne tried to override that precedent by himself crowning his son Louis the Pious in Aachen, but the principle of Papal coronation survived and was renewed in 962 when Otto I restored the Empire and its rituals after decades of turmoil.