Oh, THAT old trick!
Much better variation is to make a loop, stand on the loop with both feet spread apart, it's twice as stable. In the 70's Polaroid distributed a "handy hints" sheet in their SX-70 film packs showing how to do this, I took the pictures of the model.
If you shoot handheld panos, wrap the string around the lens and use the weight as a pointer to a spot on the ground to keep centered on the rotation point. A short 1/4" wood dowel inserted into the tripod thread hole will help you keep a consistent tilt and level.
