This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.
Forward Bend Asanas gathers three postures of the hatha yoga repertoire, two of them built on the same tortoise image and the third named instead for a direction of the body.
Kurmasana, the tortoise, has the Hatha Yoga Pradipika press the crossed ankles against the perineum and sit steadily, the body drawn in and compact the way a tortoise withdraws its limbs, an image of withdrawal that echoes the wider literature's figure for senses pulled back from their objects. The Gheranda Samhita carries it and lists a second, stretched form immediately after it.
That second form, Uttana Kurmasana, is named the tortoise turned upward, but the classical texts describe it not as entered from Kurmasana itself: the Hatha Yoga Pradipika has it follow directly from the cockerel posture, kukkutasana, the practitioner holding the lifted lotus of that pose, taking hold of the neck and rolling back to lie on the spine with the legs still bound. Both the Pradipika and the Gheranda Samhita carry it, and it is the clearest case in the classical corpus of a posture described as an entry from another rather than as a seat begun from stillness.
Paschimottanasana stretches the whole back of the body, legs extended straight, toes caught in the hands, forehead brought to the knees. Its name means literally the stretch of the west, paschima naming the back of the body as it faces west when a practitioner sits toward the rising sun. The Pradipika makes a strong claim for it, that it drives the breath into the central channel, kindles the gastric fire and makes the belly lean, claims the atlas reports as the text's own rather than as established fact. The Gheranda Samhita repeats the posture without adding to the claim.