"I have chosen for it this legend, which will be my last watchword"

Hadrian did indeed issue a denarius with the legend "Patientia Augusti," and an image of Patience personified. The precise date of this coin issue is unclear - some sources put it at 134-138 AD, which would match the interpretation Yourcenar places on it, but the British Museum consider it to be earlier (128-132 AD). No image of this coin is available. The legend is sufficiently unusual to have prompted debate, in the past, as to whether these coins were either forgeries or the result of a mistake (the intended legend, according to this theory, being "Clementia Augusti." It may have been this debate which piqued Yourcenar's interest.