What' the strangest stuff you ever found in a book?

From LitHub, an interesting research project:

There are amazing things hidden in the stacks of the University of Virginia library. In fact, there are amazing things hidden in the stacks of most libraries—which is more or less the point. At UVA, a project called Book Traces is underway to look inside every book in the stacks that was published before 1923—which, as you might imagine, is a fair number—for “interventions” that may shed light on how the books were read, studied, and used as physical objects. The interventions might be handwritten marginalia, original poetry, pasted-in newspaper clippings or illustrations, physical modifications to the book, or any one of a variety of small objects—letters, photographs, leaves, locks of hair—tucked between the pages years ago and forgotten.

As Andrew Stauffer, a professor of 19th-century-literature at UVA who started Book Traces, explained, “People have always paid attention to the marginalia of famous people, or that written in books in much earlier eras (i.e., in medieval and early modern books). But we haven’t had a way to see nineteenth and early twentieth century marginalia of the common reader, because it is mostly uncatalogued.” In addition, as libraries make moves towards digital collections and books are scanned and then discarded or stored, this kind of information will likely be lost—a love letter tucked into a novel might just be thrown away because it was blocking the text.

Book Traces has a blog, here. 

A bookstore in New York has an exhibit of stuff found in its books. There is also an interesting blog on the topic.