The Ashtanga yoga or eight limbs of yoga , which are codified in the Yoga Sutras , provides practical guide lines for achieving the goal of yoga i.e absolute silence ( samadhi) by controlling the mind.
Astanga Yoga – Eight Constituents of Yoga
LORD PATANJALI SAYS:
“Codes of self-regulation (yama) , self-disciplines (niyama), postures (Asana- physical discipline),expansion of the breath and prana for mental disciplines (paranayama), withdrawal of senses (Pratyahara- discipline of the senses), concentration (dharana) , meditation (dhyana) and samadhi (absolute silence) are the eight limbs of yoga.As impurities are eliminated through the observance of eight steps of yoga, a flame of knowledge occurs up and discriminatory wisdom is aroused.”
By observance of yamas and niyamas , ill-mindedness and impediments on yogic path are overcome.By perfection and mastery of asanas , dualities in mind cease and unsteadiness , swaying and shaking during meditation is eliminated.By practicing paranayama , it leads to illumination of mind and such mind is fit for pratyahara and dharana.By pratyahara practice , absolute control over the senses is gained.Pratyahara leads to dharana and continuity of dharana transforms into dhyana automatically .
If the dhyana is prolonged time wise, lenght wise and width wise, it transforms into samadhi. The trinity of dharana, dhyana and samadhi get integrated as one and this is known as samyama Samyama brings prajna (full illumination) and seer gets immersed into the light of his own awareness.