In 1968 pop artist Ulrich Timm created a piece of art called "Ceci n'est pas une pipe de Magritte".

It is a pipe of exactly the type Rene Magritte pictured in "The Treachery Of Images" in its original wooden case. On the inner side of the lid is a copy of Magritte's work, the sentence—now referring to the real pipe in the case—expanded to:

Ceci n'est pas une pipe de Magritte

This closes the circle Magritte opened. From the "real" pipe to a painting of a pipe (which is not a pipe), back to a real pipe which obviously is a pipe, but not one by Magritte; neither the real one not the picture of the pipe in the lid. This is by Ulrich Timm.