AaaSana : Bhujangasana, or Cobra Pose:

From Book of Yoga Made Easy : In service of Human Being 

(with Thanks)

Method: 

Lie face down on the mat, forehead touching the ground, with arms bent so that
the elbows point upward and the palms rest on the ground just below the shoulders.
Stretch the legs well out, keeping them stiff and straight, with the soles pointing upward.
Do not allow the knees to slacken or bend. Now raise the head slowly, as high as
possible, jutting the chin forward, feeling the stretch. Lift chest and torso off the ground,
pressing down on the hands but letting the contraction of the back take most of the strain.
Feel pressure traveling down the spine all the way to the sacral region. Make sure your
body from the navel to the toes rests on the floor. When you are finally upright, like a

cobra poised to strike, retain the pose for as long as possible without feeling undue strain.

Increase the time gradually from a few seconds to a full minute. Then slowly return to the
face-down position. Relax and rest.
In time you will be able to dispense almost entirely with support from the hands and
arms, although at first this may seem not even remotely possible. However, once
perfected this asana gives great benefit even though it need be performed only once a
day.

Benefits and Value: 

An exercise to make the spine amazingly supple and flexible, at the
same time it revitalizes abdominal muscles. Kidney, liver and pancreas are stimulated so
that the appetite improves and bodily heat increases. This asana is of great value to
persons who do a great deal of stooping--sedentary workers and women overburdened
with housework--and all who suffer from habitual backache.
 

Caution:  

If your spine is stiff, proceed cautiously. Remember that whereas a smooth slow
stretch will benefit you, a wrench may be painful or even harmful.