Legend has it that the demigods were once cursed because they insulted a sage. Out of this curse came a war with the demons in which many demigods were slain. Normally demigods possessed mystical powers that could bring life back to the dead, but with this curse came the inability to do this for their comrades They looked to Brahma for help. Brahma realized, however, that this was beyond his powers and told them to seek out Vishnu for the help they so desperately needed. They found Vishnu lying on the serpent Ananta in the ocean of possibility.
Vishnu advised the demigods to call a truce with the demons. He realized that there was one thing that both parties could get on board with- producing amrita, the nectar of immortality. Vishnu recommended that they churn the cosmic ocean. First they would need to move the ocean to the great mountain Mandara and use it as a churning rod. They did this, using the king of serpents, Vasuki, as a rope.
The demons pulled the tail and the demigods pulled the head of the serpent. As it began to churn, the mountain started to sink into it. At this point Vishnu appeared in his tortoise form and held the mountain on his back. The churning continued. Instead of nectar though, poisons came from the ocean. The demigods and demons called on Shiva to help. He did so by drinking the poison, which turned his throat blue. The ocean returned to its divine state.
Next from the ocean came a precious jewel, nymphs and a divine cow. Lakshmi, the goddess of fortune and consort of Vishnu also came out of the churning. Finally, Dhanvantari, the doctor of immortality, came with the nectar. Immediately the demons stole it away. But then, Vishnu came on the scene in the guise of a beautiful woman who enchanted demons and demigods alike. She said that she would distribute the nectar evenly amongst all. By the time she came to the demons, though, the nectar was gone.
The path of the yogi is to churn the body with the rope of the mind with repeated practice. While purifying, much debris comes to surface. Stick with it though, as the nectar will follow.
To take kurmasana, sit on the floor with the legs in about a 90 degree angle. The arms are placed under the bent knees and reach to the back of the body with the palms facing the floor. Ideally the torso and head will lie flat on the floor (in time!).
To take it even further, the hands can clasp behind the back and the feet can come behind the head in supta kurmasana, shown here:
This pose isn’t for everyone. It requires a great deal of lengthening through the back, shoulders and hamstrings. Always remember that you never want to force yourself into a pose. Breath yourself gently into it and over time you will achieve your goal.