History of the Roman Empire from this point on, leading his biographers to label him as insane. Most of what history remembers of Caligula comes from Suetonius, in his book "Lives of the Twelve Caesars". According to Suetonius, Caligula once planned to appoint his favourite horse Incitatus to the Roman Senate. He ordered his soldiers to invade Britain to fight the Sea God Neptune, but changed his mind at the last minute and had them pick sea shells on the northern end of France instead. It is believed he carried on incestuous relations with his three sisters: Julia Livilla, Drusilla and Agrippina the Younger. He
Holy Roman Emperor office. Starting with Ferdinand I, all successive Emperors forwent the traditional coronation. The interregnum of the Holy Roman Empire is taken to have lasted from the deposition of Frederick II by Pope Innocent IV (1245, alternatively from the death of Frederick 1250 or the death of Conrad IV 1254) to the election of Rudolf I of Germany (1273). Rudolf was not crowned emperor, nor were his successors Adolf and Albert. The next emperor was Henry VII, crowned on 29 June 1312 by Pope Clement V. The Emperor was crowned in a special ceremony, traditionally performed by the Pope in Rome.