This edition of Isaac Newton’s Philosophiae naturalis principia mathematica was created by Didier Mutel out of very thin sheets of concrete. The volume is housed in a case covered in gulachat, a rare type of leather made of skate skin. The thin concrete pages are extremely fragile – this is possibly the most fragile book in our collections.
https://fcaw.library.umass.edu/F/?func=direct&doc_number=012126096&doc_library=FCL01