Modern yoga as exercise has often been taught by women to classes consisting mainly of women. This continued a tradition of gendered physical activity dating back to the early 20th century, with the Harmonic Gymnastics of Genevieve Stebbins in the US and Mary Bagot Stack in Britain. One of the pioneers of modern yoga, Indra Devi, a pupil of Krishnamacharya, popularised yoga among American women using her celebrity Hollywood clients as a lever. The majority of yoga practitioners in the Western world are women. Yoga has been marketed to women as promoting health and beauty, and as something that could be continued into old age. It has created a substantial market for fashionable yoga clothing. Yoga is now encouraged also for pregnant women. The yoga author and teacher Geeta Iyengar notes that women in the ancient Vedic period had equal rights to practice the meditational yoga of the time, but that these rights fell away in later periods. The Indologist James Mallinson states that the Gorakhnati yoga order always avoided women, as is enjoined by hatha yoga texts such as the Amritasiddhi, the Hatha Yoga Pradipika, and the Gheranda Samhita; but all the same, women are mentioned as practising yoga, such as using vajroli mudra to conserve menstrual fluid and hence obtain siddhi. The yoga scholar Mark Singleton notes that there has been a dichotomy between the physical activities of men and women since the start of European gymnastics (with the systems of Pehr Ling and Niels Bukh). Men were "primarily concerned with strength and vigor while women [were] expected to cultivate physical attractiveness and graceful movement." This gendered approach continued as the practice of yoga asanas became popular in the mid-20th century. A masculinised form of yoga grew from Indian nationalism, favouring strength and manliness, and sometimes also a form of religious nationalism, and continues into the 21st century among Hindu nationalists like the Rashtriya Swayamsevak Sangh, continuing the tradition of gymnastics and bodybuilding exemplified by early-20th-century figures like K.