I came across this little bit yesterday, but while I typed out the text from the handwritten note that was posted, I forgot to save the URL. So this isn't original with me:
"While sitting at your desk, lift your right foot off the floor and make clockwise cirles. Now, while doing this draw the number "6" in the air with your right hand. Your foot will change direction and there's nothing you can do about it."
The best I could do was have my foot go from side to side, which is a change in direction. It also works with the left hand and foot. But if you do opposite hands and feet, you can keep your foot going clockwise while the hand draws a 6.
Also, if you reverse directions - make the foot go counterclockwise while the hand draws clockwise, you get the same results. Or I should say, at least I do.