There are a number of Upanishads describing the philosophy and the practice of yoga. Among them, Shandilya Upanishad, Yogabindu Upanishad, Yogatattvopanishad are a few to mention.
The Upanishads emphasizes the importance of devotion in the practice of yoga and meditation. In the Upanishads, Tapas is a more popular spiritual practice.
Maharshi Pathanjali is known as the founder of Yoga Darshana. Yoga Darshana which is also referred to as the aphorisms of yoga. His book on yoga is called Yoga Sutras. This book Yoga Sutras has four chapters in it. They are Samadhi Pada, Sadhana Pada, Vibhuthi Pada and Kaivalya Pada.
Hatha Yoga Pradipika is a classic text of the practice of Hatha yoga. Hatha yoga is one of the most important forms of Yoga. Here, the samadhi is reached by the purification of the body by physical movements and of course with extensive, popularly known as violent movements.
Siva Samhita is a classic text of yoga. The author of Siva Samhita is not known. The text is written like an address of Siva to his consort Parvathi; a conversation between Siva and Parvathi. Siva Samhita is regarded as a complete set of writings on Hatha yoga. There are five chapters in Siva Samhita.
Gheranda Samhita written around 17th century AD is one of the earliest texts where one can find the descriptions of asana, mudra, pranayama, neti etc. In Gheranda Samhita, Sage Gheranda teaches Yoga Chanda Kapali in the form of a dialogue. The Gheranda Samhita describes the seven types of yoga practices.