In His Kapila avatara, Lord Narayana explains the concepts of Prakriti, Purusha and Iswara, said P.T. Seshadri in a discourse.
Purusha is the jiva. Purusha is present in every body. Purusha is neither created nor destroyed. Twenty four tattvas constitute Prakriti. The five elements — water, air, ether, earth and fire; five tanmatras — sabdha (sound), sparsa (touch), rupa (form), rasa (taste) and gandha (smell); moola prakriti — manas (mind) ahamkaram (ego), mahath (unknowable) and avyakta (unseeable); karmendriyas and jnanendriyas — all of these constitute prakriti. So we have a total of 24 tattvas that constitute Prakriti.
Devahuthi wants to know what is meant by atma. Kapila replies that atma is different from Prakriti. He says to get out of the cycle of birth and deaths one must have tattva jnana, vairagya, tapas and bhakti. He then explains what bhakti yoga is. Bhakti yoga leads to atma jnana. He elaborates on ashtanga yoga, which is a part of bhakti yoga. As the name implies, ashtanga yoga has eight components — yama, niyama, asana, pranayama, pratyahara, dhaarana, dhyana and Samadhi.
Yama includes ahimsa, honesty, not stealing, Brahmacharya vrata, not killing, patience and silence. Niyama includes bathing, japa, deva puja and pilgrimages. Asana involves sitting on darbha grass and doing asanas like Sukhasana and Padmasana. Pranayama has three components — pooraga, kumbaga and rechaga. Pooraga is inhaling through one nostril; kumbaga is keeping the air inside for a few seconds and rechaga is slow exhalation.
If one does these three, the body and mind will be pure.