Historians have unanimously credited Christopher Wren with having constructed a weather clock (a self-registering instrument) in the early 1660s. This conclusion was based on the account of the French diplomat Balthasar de Monconys, which included a sketch uncannily similar to an undated drawing by Wren of the weather clock. By critically re-examining the available sources, I argue that one can infer that Wren never actually constructed a weather clock. What Monconys saw and sketched was, in fact, a drawing produced by Wren for a meeting of the Royal Society that took place on 8 January 1662. I further show that there is strong evidence to assume that Wren's drawing for the Royal Society is the undated drawing preserved at the Royal Institute of British Architects. The new context in which I place Wren's drawing provides an incentive to look at it with fresh eyes. Though the drawing does not represent a device actually constructed by Wren, it still bears (unexpected) connections to the material world that surrounded him. The analysis of the drawing developed in this article will be relevant for historians interested in the role that images can play as historical evidence.