Patanjali Yoga Sutra: Samadhi Pada

Patanjali muni wrote the following due to great daya on human beings:

After doing Sarirasuddhi and obtaining kaya siddhi, and through that and favourable to this a vaidya sastra, and after doing vak Suddhi and from that achieve sabdha brahma upasana to give wellness, and for this vyakaraṇa of panini grammar, to cleanse manas and attain kaivalya, this yoga-sutra.

Important attributes are achievements of yoga-sastra are:
1. svarupa of yoga-sadhana
2. Super natural power one gets as side effects
3. siddhi and kaivalya

In these matters upanishad and yoga-sastra do not have any contradiction. In fact, yoga is a tool to achieve the tatva of upanishad and to see them by oneself. The clashes come because yoga takes sankya sastra as base. Yoga and sankya have many differences, with sastra and upanishad. in some important matters yoga-sastra and upanishad do not agree on certain views.

CHAPTER SUMMARY 
SutrA 1,2:  Defines yogaḥ
SutrA 3,4:  Options for awareness
From Sutra 5 to 11: Description of vrrtti
From Sutra12 to 16: How to control vrrtti by abhyasa (practice) 
SutrA 17,18: Division of samadhi into samprajnata and asamprajnata
SutrA19: Some discussions on other states that resemble the samadhi
SutrA 20 to 22:  How to attain samadhi some pointers
Sutra 23:  Introduction of Ishvara and He is the easy method of attaining samadhi
SutrA 24 to 26: His nature
SutrA 27 to 29: Chanting Ishvara’s name
SutrA 30 and 31:  Distractions of manas (Mind) and their accompanying effect.
SutrA 32 to 40: Meditation on any object to combat these distractions
SutrA 41 to 45: Concept of samapatti and its varities
SutrA 46 to 48: Fruits of samapatti
SutrA 49: Object of samapatti, discussion of samaprajnata – samadhi
SutrA 50, 51: asamprajnata samadhi