When Dorigen's friends console her in The Franklin's Tale, the Franklin says that their words take effect in the same way that engraving makes an impression in a stone. This comparison recalls a similar analogy found in Boccaccio's Il filocolo, and cited there from Ovid's Ars amatoria, which holds that a lover's petitions will move his lady in time, just as dropping water hollows out hard rock. In the first part of this article, I trace the history of this analogy from the Ovidius minor to its appearances in the work of Chaucer's contemporaries. Ovid and his medieval inheritors recognized that the analogy could motivate many different kinds of persistent speech, from lovers' complaints to petitionary prayer, but they also sought to qualify its overstated claim that a speaker might reshape a listener's desires by sheer persistence, and to suggest instead that persistent speech might be a good in itself, an opportunity for creative expression and for the cultivation of virtue. In the second part, I argue that The Franklin's Tale continues to think in terms of this analogy as its characters test their own powers of persistent speech. Dorigen comes to reappraise it as she complains about the black rocks and discovers that stone can resist erosion and petition for a long time, but Aurelius goes to great lengths to avoid this kind of realization and to sustain the illusion the analogy encodes, that a persistent speaker can "emprent" his desires on other people.