Hi, Chris,
You remembered correctly. Marie said that she sleeps with a copper ring behind her head when she travels. She said if you put them under your bed you want enough of them to go from the top of your head down to your feet. If you're using the large rings you probably need 3 or 4 of them.
I don't know whether the effect of the ring is the same if you sleep with it down at the foot of your bed as opposed to up by your head.
