I had seen this illusion before but for some reason never really focused on it before. Today I saw it on Coach Burke's site and actually read the info. This exposure caused me to search out some additional info and create this post.
This is Roger Shepard’s “Turning the Tables” illusion. Look at the two tables below. If I told you they had an equal surface area on their table tops, you'd probably say "maybe". But what if I told you that they also were identical in both length and width. Don't believe me? Measure them for yourself. This optical illusion appeared in the Jan. 2003 issue of Discover Magazine.
The below image is given so you can print it out, make a cutout of a tabletop, and reposition it over the other one.
Click on picture to go to another solution page for this illusion.