Sometimes the most interesting thing about a story is what is left unsaid… or uneaten.

A tweet by the Cambridge University Library Special Collections account has been circulating ever since one employee made an unusual find in a 1529 edition of a manuscript by Augustine: a partially eaten cookie.

Today’s unexpected discovery in a 1529 volume of Augustine. For future reference, we have acid free paper to mark your place. Please don’t use baked goods. pic.twitter.com/YGiLDTjmSk — Cambridge UL Special Collections (@theULSpecColl) February 21, 2020

It’s unclear why such a delicious snack was 1) not fully eaten 2) used as a bookmark, but the sizable stain around the cookie would suggest that it has been there for quite some time—perhaps as long as fifty years. Blech.

The manuscript had been donated to the library’s Special Collections in 1970. Emily Dourish, the librarian who found the cookie, told The Scottish Sun her theory about what may have happened at the grammar school that held the manuscript before it was given to Cambridge.

“It was probably a schoolboy looking at the book over 50 years ago who then accidentally dropped a biscuit and it was forgotten about,” she said.

Who knows if that’s true, but if it is, maybe the kid got spooked at the thought of how much trouble he’d be in if he were found out.

The point here is that you should fully eat everything that you ask for and, if half of that falls into a rare manuscript, probably don’t leave it for future generations to find.