Samadhi — The Dissolution of the Observer
Samadhi is the culminating state of meditation — the complete dissolution of the separation between the meditator and the object of meditation into unified, boundless awareness.
Samadhi (literally 'putting together,' 'union') is the goal of all Tantric and Yogic practice — the complete dissolution of the subject-object dichotomy in unified, boundless awareness. The Yoga Sutras distinguish multiple levels: Savikalpa Samadhi (with thought — awareness united with an object while retaining the trace of observer), Nirvikalpa Samadhi (without thought — complete dissolution of all mental modifications into pure awareness), and Sahaja Samadhi (natural Samadhi — the continuous, effortless abiding in non-dual awareness during all activities). Kashmir Shaivism's Turiyatita corresponds to Sahaja Samadhi — the non-dual awareness that no longer requires meditation to maintain itself but pervades all states continuously.
In Samadhi, the meditator, the act of meditation, and the object of meditation become one. This is the fruit of all practice.
Patanjali distinguishes savikalpa (samprajnata) samadhi, still holding an object, from nirvikalpa (asamprajnata), in which even that support drops away; Kashmir Shaivism's Sahaja Samadhi extends this into unbroken awareness during all activity.
Yoga Sutras of Patanjali