The Hatha Yoga Pradipika, the most important premodern text on physical yoga, is a 15th-century Sanskrit manual by Svatmarama, who assembled it out of older hatha texts and traced the teachings back to Matsyendranath and the Natha yogis. Pradipika means lamp, or light, so the title reads as something like light on hatha yoga.
It has four chapters. The first covers asana and describes fifteen of them, with the seated postures getting the most attention. The second turns to pranayama and the cleansing practices, including nadi shodhana, ujjayi, bhastrika, and kapalabhati. The third describes mudra and bandha, the fourth arrives at samadhi. Svatmarama presents all of it as preparation, the body and breath made ready for the meditation Patanjali lays out in the Yoga Sutras.
The text was written for renunciates with time on their hands and a teacher nearby, and some of it sounds strange to us today. There are rules about diet, cleansing practices involving cloth and salt water, and confident claims about what breathing will do to your body. I don't teach from it directly, it it's a useful record of how one lineage thought about the body, and check anything against your own experience before you adopt it.
A critical edition and translation of the Haṭhapradīpikā is available online:
Birch, Jason, James Mallinson, Jürgen Hanneder, Mitsuyo Demoto, and Nils Jacob Liersch. Haṭhapradīpikā Critical Edition and Translation. 2024. hathapradipika.online.