The limb nobody talks about
Patanjali lists svadhyaya as the fourth of the five niyamas in the Yoga Sutras, Book II. The niyamas are personal observances, the inner code of conduct that precedes any posture, any breath-work, any meditation. Saucha, santosha, tapas, svadhyaya, Ishvara pranidhana. Most people who have done a yoga teacher training can recite that list. Almost none of them were taught what svadhyaya actually demands.