Foundations of Yoga: History, Streams and Classical Texts
The textual spine
Yoga's literature moves from the Vedic corpus and the Upanishads (Katha Upanishad's definition of yoga as steady restraint of the senses) to the Bhagavad Gita, which presents karma yoga, jnana yoga and bhakti yoga as paths, with chapter 6 devoted to dhyana yoga. The classical systematisation is Patanjali's Yoga Sutra, arranged in four padas with roughly 196 aphorisms, defining yoga as citta-vritti-nirodha and giving the eight limbs.
Hatha literature is separate and later: the Hatha Yoga Pradipika of Svatmarama (about the 15th century CE) has four chapters covering asana, pranayama, mudra and samadhi, and closes with nadanusandhana. The Gheranda Samhita teaches a seven-limb (saptanga) path: shatkarma, asana, mudra, pratyahara, pranayama, dhyana, samadhi. The Shiva Samhita and Goraksha Sataka belong to the same natha stream.
Streams
Know jnana, bhakti, karma and raja yoga as the classical four, with hatha, mantra, laya and kundalini yoga treated as distinct approaches. The root yuj means to yoke or unite.
Traps
Examiners blur Patanjali's eight limbs with Gheranda's seven; remember ashtanga versus saptanga. Candidates wrongly claim Patanjali detailed dozens of postures - his asana limb is famously brief (sthira sukham asanam). Another frequent error: crediting the Yoga Sutra with kriyas or chakras, which are hatha material.
Rule of thumb
Four, four, seven - Patanjali four padas, Pradipika four chapters, Gheranda seven limbs. Anchor any text question to that skeleton.