The eight limbs (ashta anga) of yoga present a road map for spiritual practice, beginning with yama (prohibitions) and niyama (injuctions) which are intended to purify one's mind (sattva shuddhi), then asana, posture, required for long periods of seated meditation, then pranayama, breathing exercises, pratyahara, sense withdrawal, dharana, concentration, dhyana, meditation, all leading to samadhi, a mystical state of absorption.