are supported by evidence of varying quality, from case studies to controlled trials and ultimately systematic review of multiple trials. Magical powers Medieval authors asserted that Haṭha yoga brought physical (as well as spiritual) benefits, and provided magical powers including of healing. The Hatha Yoga Pradipika (HYP) states that asanas in general, described as the first auxiliary of haṭha yoga, give "steadiness, good health, and lightness of limb." (HYP 1.17) Specific asanas, it claims, bring additional benefits; for example, Matsyendrasana awakens Kundalini and helps to prevent semen from being shed involuntarily; (HYP 1.27) Paschimottanasana "stokes up the digestive fire, slims the belly and gives good health"; (HYP 1.29) Shavasana "takes away fatigue and relaxes the mind"; (HYP 1.32) while Padmasana "destroys all diseases" (HYP 1.47). These claims lie within a tradition across all forms of yoga that practitioners can gain supernatural powers. Hemachandra's Yogashastra (1.8–9) lists the magical powers, which include healing and the destruction of poisons. Biomedical claims for marketing purposes Twentieth century advocates of some schools of yoga, such as B. K. S. Iyengar, have for various reasons made claims for the effects of yoga on specific organs, without adducing any evidence. The yoga scholar Suzanne Newcombe argues that this was one of several visions of yoga as in some sense therapeutic, ranging from medical to a more popular offer of health and well-being. The yoga scholar Andrea Jain describes these claims of Iyengar's in terms of "elaborating and fortifying his yoga brand" and "mass-marketing", calling Iyengar's 1966 book Light on Yoga "arguably the most significant event in the process of elaborating the brand". The yoga teacher Bernie Gourley notes that the book neither describes contraindications systematically, nor provides evidence for the claimed benefits. Jain suggests that "Its biomedical dialect was attractive to many." For example, in the book, Iyengar claims that the asanas of the Eka Pada Sirsasana cycle The history of such claims was reviewed by William J. Broad in his 2012 book The Science of Yoga. Broad argues that while the health claims for yoga began as Hindu nationalist posturing, it turns out that there is ironically "a wealth of real benefits". Evidence-based medical claims Researchers have studied the medical and psychological effects of yoga as exercise in a wide range of trials and observational studies, sometimes with careful controls, providing evidence of differing quality about yoga's possible benefits. The physician and yoga therapist Timothy