This imagination exercise is sometimes known as the heavy/light hands test. It involves experiencing a levitation in one arm, which is contrasted with an experience of weight or fatigue in the other.
"What I would like you to do is extend your arms out in front of you, like so… and you can place your left-hand palm-up, with your right hand facing palm-down.
"Perfect. And now just go ahead and close your eyes.
"And you can now imagine a huge helium-filled balloon tied to this wrist [taps slightly under right wrist], tugging at the arm. Maybe go ahead and imagine 10, 15, 20 bright red helium balloons, rising up into the air, taking that arm with it.
"And on your right hand, you can imagine a heavy hard-back dusty library book... feel that weight on your hand.
"And as you feel your right hand getting heavier and heavier, your left hand is floating higher and higher, floating upwards with those balloons...
"As I place another heavy book on that right hand, getting heavier and heavier now...
"As that left hand continues to rise..."
At the appropriate point, you can invite them to open their eyes and look at their hands. Even for those people who experience little movement, they are usually surprised by the contrasting position of their hands.