“In this Sūtra, Patañjali lists the five types of mental activities:
Pramāṇa Vṛtti, Viparyaya Vṛtti, Vikalpa Vṛtti, Nidrā Vṛtti, and Smṛti Vṛtti.
Vṛtti and Pariṇāma are synonymous, meaning “change of form”.
These five Vṛtti represent changes in the characteristics and functions of the mind.”
– T Krishnamacharya on Yoga Sūtra Chapter One verse 6

“Although the activities of the mind are countless,
Patañjali categorizes all of them in one of five groups:
Pramāṇa, Viparyaya, Vikalpa, Nidrā, and Smṛti.”
– T Krishnamacharya on Yoga Sūtra Chapter One verse 6

“The five groups are
right perception,
wrong perception,
imagination,
deep sleep and
remembrance.”
– Paul Harvey on Yoga Sūtra Chapter One verse 6

“Nidrā or deep sleep is the state in which the
mind’s link with external stimuli is cut off.
In this state, Tamas is dominant.
Although in deep sleep the mind
has no link with anything external,
this does not exclude all links,
which is why we are often able to recall
whether our sleep was sound or disturbed.”
– T Krishnamacharya on Yoga Sūtra Chapter One verse 10

“Deep sleep is the fluctuation of obscuration,
supporting an absence of mental activity.”
– Paul Harvey on Yoga Sūtra Chapter One verse 10

“In Sūtra 1.10 Patañjali defines Nidrā as a
Citta Vṛtti or, a specific type of cognition, one
where Tamas is the object, to the point where
the mind’s link with external stimuli is cut off.
How do we discern between states such as
Pratyāhāra as a disengagement, or Samādhi,
where one is as if empty of one’s own character,
and what is seen as the experience of Tamo Nidrā?”
– Paul Harvey on Yoga Sūtra Chapter One verse 10

“Sleep and Samādhi are the only times when there is no ‘I‘.”
– TKV Desikachar on Yoga Sūtra Chapter One verse 10

“The state of Dhyānam is possible in a seated posture.
If a person lies down, it may induce sleep.
If a person walks and moves about,
he may be distracted by the objects around him.
This posture must be in a place
where the mind will not be distracted.”
– T Krishnamacharya on Yoga Sūtra Chapter Three verse 2

Links to Related Posts:

• T Krishnamacharya Yoga Sūtra Study Quotes Collected and Collated
• TKV Desikachar Yoga Sūtra Study Quotes Collected and Collated
• Paul’s Yoga Mālā – A Thread of Pearls from Patañjali’s Yoga Sūtra
• Paul’s Yoga Sūtra Study Keywords – Collected & Collated into Chapters
• Paul’s Yoga Sūtra Study Questions – Collected & Collated into Chapters