'Consider a lake. Does the water touch the bank on one side and not on the other, or does it touch the banks equally? When you are performing an asana, your consciousness, like the waters of a lake, should touch the frontiers of the body everywhere.
Where, then, is there room for thoughts to arise? How can there be a thought arising when you are doing a perfect asana - when your intelligence has spread through your whole body?'
BKS Iyengar - author of Light on Yoga, Light on Pranayama, and founder of the Iyengar school of yoga