Nothing

The Swedish writer Biger Vikström wrote in 1958 a short-story called 'En Kofés'. He describes a man who enters a lumber-workers camp and finds them busy at work whittling small objects. Surprised at the abandonment of usual activities like card-playing or story-telling, he asks the cook to explain what is going on. The cook says that they are whittling Kofés, which are objects that need to be executed following two rules:

A Kofés may look anyway.

A Kofés may not resemble anything but itself (it may not resemble any dead or living thing).

The challenge seems easy at first and the man gets totally absorbed whittling. The first rule is easy enough, but the second one starts to pose problems as the man cant keep forms from materializing in his piece. No matter what he does he keeps seeing limbs or objects take shape in the wood. He slowly realizes the futility of his attempt and gives up.