Some were expressions of gratitude for favors received, and others outright bribery for favours expected in return.
The Praetorian Guard, intimate to the emperor's person, was an even greater threat to security.
Emperor Augustus bequeathed the Praetorian Guard a substantial sum in his will, but it was not until the reign of Tiberius that gifts of money were thought to be mandatory.
Each Praetorian Guard received 10 gold pieces in return for not defending Sejanus.
The inevitable result of the custom of the donativum was the Guard's auctioning of the empire to Didius Julianus in 193.