I believe I accidently left a few hundred dollars along the spine of one hardcover I donated to Goodwill.
Speaking of spines of books, last I saw it mentioned, archive.org apparently wasn't digitizing an image of the spline edge of books. If that seems like a missed opportunity to facilitate actual "bookshelf" views.
The introduction to the edition of The Leopard that we have remark that the author and his wife were used to stashing important papers--letters, high-denomination bills, what have you--in their many books. Some they then forgot and lost.
I did once find a $20 I had left in a book; movie tickets and a postcard are about all I can remember finding of someone else's leavings.
Did you fold the bills so that you could slip them down between the cover and the spine?
Yes, folded once between the cover and spine. My one consolation is that it was probably Jowett's translations of Plato -- on the possibility that that would have been less likely to go straight to trash at Goodwill.
1. It's written specifically to one Jacob Watson, whose signature appears on the back like a modern personal check. The written amount is $5500--, and below that is added "5000 discounted", which I take to mean the note was already (mostly?) cashed.
2. I used to follow someone online who worked as a scanner for IA and sometimes posted behind-the-scenes stuff including a few weird finds. (I can't name-drop since she hasn't worked with IA for a few years now, but maybe somebody else knows someone.) That might be the best bet since the process is largely automated and there's not a lot of time to document and compile incidentals like that.
Speaking of spines of books, last I saw it mentioned, archive.org apparently wasn't digitizing an image of the spline edge of books. If that seems like a missed opportunity to facilitate actual "bookshelf" views.