From the Fifth Nail "The Nail of the Zero-Sized Reality Body" of the Twenty-One Nails
Sound means natural sounds. Light means natural form or body. Rays mean natural thoughts. These are the natural sounds, lights, and rays of ripga.
First, relax. Breathe in and out a long breath. Close your eyes. Bring your attention to your body. Feel the stillness of the body. Feel the sensations of the body. Feel the sensations of the upper body parts. Feel the stillness of the upper body parts. Feel the sensations of the lower body parts. Feel the stillness of the lower body parts.
Now try to transform the upper body parts into light. Feel the stillness of the upper body light. Now transform the lower body into light. Feel that stillness of the light. Now listen to empty sound. Feel that empty sound of rigpa. Listening, the silent sound of rigpa. Now transform your consciousness as rays. All thoughts transform into rays of rigpa. Feel the rays. Now your body is transformed into self-light of rigpa. And your sound or speech is transformed into self-sound of rigpa. All your thoughts of consciousness are transformed into self-rays of rigpa. Feel this. Keep this condition continuously.
[Five minutes of silent practice]
Now feel that light of the body. Slowly, slowly, the light dissolves into the center of the heart where the rigpa abides. Now slowly, slowly, empty sound dissolves into the center of the heart. Now slowly, slowly, rays of the thought dissolve into the center of the heart.
Now relax, breathe slowly. Open your eyes, and simply relax.