Manneken Pis, a Renaissance fountain in Brussels depicting a urinating boy, is a "floating signifier", attracting multiple symbolic meanings from its earliest appearance. There is a surprising degree of overlap between meanings attached to the statue by hermetic alchemists and those used in health promotion campaigns. Approaches to alchemy could be scientific or spiritual but shared symbolic modes of expression. Both alchemists and public health promoters see the statue as capable of inspiring practical changes in behavior in an individual. From the starting point of an account of an eighteenth-century search for the philosopher's stone which is said to have ended in a tragic death, this article examines how alchemists and proponents of public health have used the image of the urinating boy.