Here's a problem (8.32, Deflections in Bending) I remembered from "An Introduction to the Mechanics of Solids" by Crandall & Dahl. A most wonderful book, and the authors have a sense of humour to boot. Given that the first edition of this book was in 1959, and that this problem is rather basic, chances are that this was one of the first textbooks to carry this joke :-)
The signpost reads "Plan Ahead". ROFL!!