“Let us examine the Yoga Sūtra……
In the 3rd chapter there is the idea of Saṃyama (C3 v4) or the Sādhana of regularly involving the attention of the person towards a specific object or idea.
There are certain Sūtra which tell us of certain powers or clarity developed through Saṃyama.
When a person has reached a certain level of attention he can pursue one examination within his individual capability for a certain period of time.”
– TKV Desikachar France 1983

“Saṃyama can be on the physical, as in Hasta on the strength of an elephant.
Or Saṃyama on Saṃskāra,
an investigation of mental tendencies leading to an understanding of past traits.
Or on Grahaṇa,
going into the idea of how the senses hold objects,
what is the basis inside for sense perceptions.
This leads to Indriya Jaya.
Patañjali is giving indications that these practices are possible.
Īśvara Praṇidhāna is quoted more than once, through investigation of this idea he tells us that it is this that makes a person aware of their true self
– Tataḥ Pratyak Cetanā Adhigamaḥ (YS Chapter One verse 29).
Sādhana can be physical, senses, mental, spiritual.”
– TKV Desikachar France 1983