This technique is called the Statue Transformation, because it involves the visualization technique of imagining yourself turning to concrete or metal. It's an effective way to completely numb the body and enter a mental zone that will bring on the state of sleep.
As we go through our day, the stress that we feel from interacting with people or situations can take a very real physical toll on our body. This results is tension in the neck and back. While we may not notice it, due to becoming used to the tension throughout the day, it is still a physical block that keeps us from falling asleep.
The visualization exercise of seeing yourself turning to stone is great way to relax the body and ease out that stress that has built up over the day.
Statue Transformation (Step-By-Step):
Turn off or dim the lights. Remove any noise distractions from the room.
Lie down in bed and close your eyes.
Begin by focusing your attention on your feet.
Feel the sensation and the blood coursing through your feet.
Now imagine your feet becoming stiff and solid, like stone or metal.
Imagine that your feet are becoming heavier and that they are becoming so heavy that they are weighing down the mattress.
Now continue to do the same thing with your legs.
Feel your legs getting stiff, solid, and heavy.
Work your way up your body (feet, legs, torso, arms, hands, neck, etc).
Imagine each part of your body becoming stiff and solid like concrete or steal.
When doing this slow mental solidification process, it's very typical that you will fall asleep before even reaching the head.
However, if you get through the entire process and have imagined all your body parts becoming stone or metal, then just lay there and exist in this state. Eventually the relaxed state of your body will take effect and you will fall asleep.