Notes: The cultivation of ekāgra or singular attention is central to the practice of yoga. In Patanjali's classic formulation, this process unfolds over four major phases: Initial pratyāhāra, the withdrawal of consciousness from externality; a basis for dhāraṇā, the mental retention of the object of concentration; leading to dhyāna, the profound and effortless flow of contemplation; and into samādhi, the unification of the mental field with the object. This initial unification of consciousness is progressively refined over the stages of recursive vitarka, reflective vicāra, intuitive ānanda, and self-imploding asmitā, and ultimately reaches nirvikalpa-samādhi, an invariant union marked by the categorical dissolution of polarized boundaries.