The Rishis had in their forest-research-laboratories discovered Variuous methods of Prolonginng life Pranayama, Asanas like Sirshasana and Sarvangasana , prayer, Havan , certain herbs, and Kaya Kalpa. they discovered that those living beings which breathed slowly , with less number of breaths per minute , live longer, and that suspension of breathing led to hibernation and prolongation of life. They prescribed Pranayama for long life.