The antiquity of the "injunction" Non plus ultra

The latinesque phrase Non plus ultra is well-known to historians of early modern science, because its antithesis-Charles V's imperial motto, Plus ultra-was a familiar catch-cry for the new science. But there is much confusion about the origins of these expressions. One common account supposes some version of the negative tag to have been a standard classical motto, an injunction perhaps, attached to the Pillar of Hercules. This phrase was later inverted to provide the Imperial device (so goes this explanation) and the resulting positive phrase was interpreted as celebrating colonial expansion across the Atlantic. Rosenthal, however, has convincingly undermined this whole story: the ancient motto it posits simply did not exist; the modern was coined before Charles acquired his association with America. The present work refines Rosenthal's argument. I uncover classical sources for the early modern motto, by invoking a more satisfactory version of the inversion thesis. I agree there was no set negative adage, but insist there was a set idea, occuring repeatedly, in texts quite familiar to the Renaissance. This idea is set in contexts that display a popular Urbild of the successful conqueror, and is eventually projected onto Alexander. So it is an ideal source for imperial propoganda.