Sarvangasana

[13][14] Iyengar devoted a whole page of Light on Yoga to the beneficial effects of Sarvangasana, claiming that the pose is "one of the greatest boons conferred on humanity by our ancient sages",[15] calling it "the Mother of asanas"[15] and "a panacea for most common ailments.

"[15] He asserted that the pose had a direct effect on the thyroid and parathyroid glands, explaining that the chin lock increased their blood supply.

[15] The soothing of the nerves in turn, he wrote, relieved hypertension, irritation, shortness of temper, nervous breakdown, and insomnia.

[15] It was useful, Iyengar claimed, for urinary disorders, menstrual problems, piles, hernia, epilepsy, low vitality, and anaemia.

[16][17] Iyengar advised against the pose for people with high blood pressure,[15] for whom he recommended halasana instead, as in his view it brought similar benefits.

Sarvangasana
The mudra Viparita Karani uses a variety of inverted poses, sometimes similar to the modern Sarvangasana, to trap and retain prana , life force, which would otherwise drip from the head and be lost. Illustrated manuscript of the Joga Pradipika , 1830
Iyengar Yoga teaches the pose using props to ensure correct alignment. [ 11 ]