Ammianus Marcellinus Res Gestae 30.5.11

[11] And so the emperor remained at Carnuntum, where throughout the entire three summer months he was preparing arms and supplies, intending, if in anyway fortune favoured, to find opportunity to attack the Quadi, the instigators of the terrible uprising. It was in that town that Faustinus, nephew of Viventius, ¹ the praetorian prefect, when serving as a state-secretary, after an investigation conducted by Probus, was first tortured and then put to death by the hand of the executioner. The charge was that he had killed an ass, as some of his accusers alleged, for use in secret arts, but as he himself declared, to strengthen the weakness of his hair, which was falling out. ²