Linnea Vegh was working at a large, well-lit workspace in the Conservation Division on a recent day, considering an unusual problem in an 1869 Persian-Arabic dictionary published in India: Snakeskin. Five thin, scaly pieces, all likely used as bookmarks that got left behind for more than a century. Welcome to the weird world of “inclusions,” an ecosystem known to archivists the world over in which they come across all sort of things readers have purposefully or inadvertently left between a book’s pages.