Doesn't work for me.....
Cross your eyes only looking at the way the two pics move. If you can't see what's going on, tilt your head to the side, then start crossing your eyes again. It should be visible that this is what's happening:
Keep your eyes crossed and make the outside pics go to the middle, horizontally overlapped (not vertically since they're offset because you've still got your head tilted). When they're overlapped horizontally, keep your eyes there and tilt your head back level. This'll bring the vertical offset to nothing and give you this, what you're supposed to see:
oops.. had it switched around.