Samadhi (Yoga Sutras)
Samadhi — unified consciousness, the eighth and highest limb — as the culminating state of Patanjali's yoga system in which meditator and object merge in pure awareness.
Samadhi (from sam = together, complete; a = towards; dha = holding) literally means 'putting together completely' or 'holding to the Divine.' As the eighth limb of Ashtanga Yoga, Samadhi is both the goal and the highest tool of the system — a state so profound that it dissolves the illusion of separate selfhood and reveals consciousness's own nature directly. In the first chapter, Patanjali maps a spectrum from Samprajnata samadhi (samadhi with cognitive support) through Asamprajnata samadhi (samadhi without cognitive support) to Nirbija samadhi (seedless samadhi) — each level progressively more free of mental content. In the third chapter, Samadhi is one-third of Samyama — the master key of yogic epistemology. In the fourth chapter, Samadhi is the state from which Kaivalya is directly accessible. It is simultaneously the highest experience and the transcendence of all experience.
When the mind alone shines, as if devoid of the meditator's own form, that is samadhi.
William James identified samadhi-type experiences as among the most significant data points for the psychology of religion in The Varieties of Religious Experience, noting their four characteristic qualities — noetic, ineffable, transient, and passive — that perfectly match Patanjali's description of the samadhi state.
Yoga Sutras of Patanjali