Another gem from Brown and Duguid, p 187:
"The Irish writer Flann O'Brien imagined a book handling service for the culturally insecure. For a fee, book handlers would crease the spines of your books, turn down pages, mark passages, put intelligent comments in the margins, or, for a slightly greater sum, insert tickets from operas or classic plays as bookmarks."
Apart from the image it creates, and particularly the idea of a price differentiated service, this is a good marker for the handling of historical evidence. I am not suggesting to budding historians that they should view every document or item as inherently false, designed to give a wrong impression, but just that every document or piece of evidence should be read with a spirit of critical curiosity. One need not assume that an opera ticket in a book is designed to mislead, but also one cannot assume that it means that the owner of the book went to that opera. And if he did, one cannot assume that he was "an opera goer" as opposed to someone who just went to that opera, and maybe slept right through it. The ticket and the book must be examined more critically than that, with attention to the possible and probable explanations, and to the context provided by other similar pieces of evidence.