The cobra pose is one of the 12 basic Asanas (postures) as taught by Swami Vishnu-devananda , founder/Sivananda Yoga Vedanta Centers
| Definition: Coiling your upper body up and back. |
Lie on your front. When you are fully relaxed, begin to come into the cobra. Still lying on your front, place your hands flat on the floor so that they are directly underneath your shoulders. Next lift your head up a little and bend your neck, then lower your forehead to the ground.
Inhale, slowly rolling up and back. First bring your forehead up so that your nose rests on the floor, then continue rolling up and back. Move slowly, so that you feel each vertebra arching back.

Hold the pose for 10 to 60 seconds. Slowly roll down, keeping your head back until last. As you do the cobra, make sure you are not overextending the lower back. No pain should be felt in the lower back. You may want to repeat it two more times.
Once you are proficient in the above steps, you can attempt some variations.