This article analyzes nonsensical mock prescriptions, especially from sixteenth- and early seventeenth-century France, situating these in a context of both medical and literary history. Mock prescriptions shed light on the writing and performance of nonsense, in particular in their use of the adynaton, and on how such nonsense appealed to a mixed audience, including that of Bruscambille. They are also prominent in representations of mountebanks and thereby provide an unusual insight into their practice. Mock prescriptions are shown to be a flexible cultural form that can be playfully adapted for literary, political, and religious purposes, for example, in Rabelais, Marguerite de Navarre, and in La Satyre Menippee.