The Roman History · Amm. 21.16.10

And if anything of the kind got wind, he instituted investigations of a more terrible nature than the law sanctioned, appointing men of known cruelty as judges in such cases; and in punishing offenders he endeavoured to protract their deaths as long as nature would allow, being in such cases more savage than even Gallienus. For he, though assailed by incessant and real plots of rebels, such as Aureolus, Posthumus, Ingenuus, and Valens who was surnamed the Thessalonian, and many others, often mitigated the penalty of crimes liable to sentence of death; while Constantius caused facts which were really unquestionable to be looked upon as doubtful by the excessive inhumanity of his tortures.

Ammianus Marcellinus · translated by C. D. Yonge · 1911 reprint
C. D. Yonge translation (preface dated February 1862); G. Bell and Sons, 1911; Project Gutenberg #28587
Passage preview. Read in context for the complete text, notes and references.