Falling into space yoga(no comments required-experiential)
If you have an extremely weak stomach then don't try this. Lay on your bed on your stomach. Lift your head, face forward, and begin moving your whole head in big horizontal figure eights (like an infinity symbol with the loops left and right) about one per second (I like to say 'One Mississippi') for maybe 20 seconds then stop. Crazy people may want to experiment with longer.