The sleeping tortoise takes all its limbs into its carapace. So does the yogi: going back into himself he does not see anything worldly any longer, he makes peace in himself.
B.K.S. IyengarThe practice of yogasana for the sake of health, to keep fit, or to maintain flexibility is the external practice of yoga. While this is a legitimate place to begin, it is not the end. Even in simple asanas, one is experiencing the three levels of quest: the external quest, which brings firmness of the body; the internal quest, which brings steadiness of intelligence; and the innermost quest, which brings benevolence of spirit.
B.K.S. IyengarYour body exists in the past and your mind exists in the future. In yoga, they come together in the present.
B.K.S. Iyengar