Oscar Reutersvärd is widely acknowledged as the father of the impossible figure.
Look at the image below. Do you see rectangles or diamonds? . . . Optical Illusions, click to see more.
Impossible Object by Oscar Reutersvärd
Oscar Reutersvard - Variations On An Impossible Triangle
zentangle triangle - Google zoeken
5. Impossible cuboids - Adventures with Impossible Figures - Impossible world
Impossible Shapes: Columns by Jeff Merrick
Luiz Sacilotto, C. 9770, 1997