You Can't Judge a Book by its Cover

The spine of this 18th-century wooden book reads Historia Universalis.  But when the book is opened, a more fundament-al purpose is revealed:

The folio opens to reveal two oaken boards that can be folded out to form a closed square and one board lifted upward to become the seat, the hole in the middle ready to hold a chamber pot. The box rests on four small wooden pegs, the binding protected by a small brass plate at the foot. Condition: clasps possibly renewed in 19th century, seat cracked, old restorations, minor losses to calf.

An unusual example of the use of the book form to disguise travelling personal furniture, probably for use on the military field.

This commode-book sold at auction in September of 2008 for $1500.

Link.