Ammianus Marcellinus Res Gestae 31.10.21

[21] At that same time Frigeridus, who was carefully making many useful plans for the general security, and was hastening to fortify the pass of Succi, ¹ in order that the roving light-armed bands of the enemy might not, like torrents swollen by melting snow, roam at large over the northern provinces, was given a successor in the person of a general called Maurus, notoriously venal under a pretence of boldness, and changeable and unreliable in all his conduct. He it was who (as I have told in my narrative of previous events) ² when Caesar Julian was in doubt about the crown to be put upon his head, with haughty cleverness took off his neck-chain and boldly offered it to him for the purpose, being at the time one of Julian’s bodyguard.