According to Patanjali there are eight “limbs” of yoga. How they work together can be understood from the following story:
Once upon a time a couple lived happily together in a country that had an unjust king. The king became jealous of their happiness and threw the man into a prison tower. When his wife came to the tower at night to comfort him, the man called down to her that she should return the next night with a long silken thread, a strong thread, a cord, a rope, a beetle, and some honey. Although puzzled by the request, the wife returned the next evening with all the items. Her husband then asked her to tie the silken thread to the beetle and smear honey onto its antennae. She should then place the beetle on the tower wall with its head facing upward. Smelling the honey, the beetle started to climb up the tower in expectation of finding more of it, dragging the silken thread as it did so. When it reached the top of the tower the man took hold of the silken thread and called down to his wife that she should tie the strong thread to the other end. Pulling the strong thread up, he secured it also and instructed her further to tie the cord to the other end. Once he had the cord the rest happened quickly. With the rope attached to the cord he pulled it up, secured one end of it and, climbing down, escaped to freedom.
The couple are, of course, yogis. The prison tower represents conditioned existence. The silken thread symbolizes the purifying of the body through asana. The strong thread represents pranayama, breath extension, the cord symbolizes meditation, and the rope stands for samadhi, the state of pure being. Once this rope is held, freedom from conditioned existence is possible.