The enigmatic collection of imperial vitae ranging from the emperor Hadrian to Carinus, spanning a period of some 170 years, has long been subject to detailed scrutiny. Dubbed Historia Augusta by Isaac Casaubon in 1603, this historical document has been recognised to be anything but historical, and therefore hardly deserves to be treated by historians as a viable document – or at least this appears to be the position held by mainstream scholars on the subject. While there are still historians who maintain that the vitae were forged by several different authors, if not exactly six as purported in the work itself, the widespread thesis is that this ‘mockumentary’ was produced by one person only, but there is little agreement on the question when. However, there remain issues which, after careful examination, admonish us that even the well-accepted one-author theory is anything but airtight, one of them being the issue of the sources, their collection and implementation in the actual narrative. Several cited documents, such as letters, senatorial decrees etc., have been proved as forgeries, but the author(s) went out of their way to cloak them in a veil of fake certainty; one such instance is the cited report on the inauguration of Marcus Claudius Tacitus. On the other hand, there are several completely vague references to some Greek book – quidam liber Graecus, which must arouse the reader’s suspicion. While this article does nothing to contest the one-author theory, it raises questions: Why, so late in the work, this change of approach in citing sources? Why not furnish the cited ‘documents’ with fabricated names?