Gaius Suetonius Tranquillus, commonly known as Suetonius (c. 69 - after 122 AD), was a Roman historian belonging to the equestrian order who wrote during the early Imperial era of the Roman Empire. His most important surviving work is a set of biographies of twelve successive Roman rulers, from Julius Caesar to Domitian, entitled De Vita Caesarum. He recorded the earliest accounts of Julius Caesar's epileptic seizures. Other works by Suetonius concern the daily life of Rome, politics, oratory, and the lives of famous writers, including poets, historians, and grammarians. A few of these books have partially survived, but many have been lost. Suetonius describes the early career of Tiberius, which included his command of several Roman armies in Germany. It was his leadership in these German campaigns that convinced Augustus to adopt Tiberius and to make him his heir. According to Suetonius, Tiberius retired at a young age to Rhodes, before returning to Rome some time before the death of Augustus. The ascendance of Tiberius to the throne was possible because the two grandsons that Augustus had died before Augustus, and the last grandson, Postumus Agrippa, although originally designated co-rule with Tiberius was later deemed morally unsound by Augustus. Augustus began a long (and at times successful) tradition of adopting an heir, rather than allowing a son to succeed an emperor. Suetonius quotes from the will Augustus left. Suetonius suggests that not only was Tiberius not thought of highly by Augustus, but Augustus expected Tiberius to fail. After briefly mentioning military and administrative successes, Suetonius tells of perversion, brutality and vice and goes into depth to describe depravities he attributes to Tiberius. Despite the lurid tales, modern history looks upon Tiberius as a successful and competent Emperor[citation needed] who at his death left the state treasury much richer than when his reign began. Thus Suetonius' treatment of the character of Tiberius, like Claudius, must be taken with a pinch of salt. Tiberius died of natural causes. Suetonius describes widespread joy in Rome upon his death. There was a desire to have his body thrown down the Gemonian stairs and into the Tiber River, as this he had done many times previously to others. Tiberius had no living children when he died, although his (probable) natural grandson, Tiberius Julius Caesar Nero (Gemellus), and his adopted grandson, Gaius Caesar Caligula, both survived him. Tiberius designated both as his joint heirs, but seems to have favored Caligula over Gemellus, due to Gemellus' youth.