The Science of Yoga

like Gandhi. He had written dozens of books on Calcutta and proved to be a treasure trove of ideas, kindness, energy, and common sense. Nair made journalism seem respectable.
    We visited historians, archives, literary societies, and more, traveling by bus, subway, bicycle rickshaw, and train (open doors, looking out over villages and smoky morning fires). He refused money. Nair explained that he did such things out of a sense of civic duty.
    Paul was a native Bengali (his given name was Nobin Chunder Pal or, in some iterations, Navina Chandra Pala or Nobin Chundra Pal) who had climbed the social ladder by virtue of a good education. The British rulers of early nineteenth-century India exploited the nation ruthlessly. But they also established schools for native youth in which the curriculum was European and the language of instruction was English. The idea was to build a class of skilled underlings to aid the empire’s administration.
    Paul represented one of the early successes. In Calcutta, the first capital of British India, he enrolled in medical school and applied himself to the city’s intellectual life. At the Society for the Acquisition of General Knowledge, a hotspot ofupward mobility, he heard lectures on such racy topics as “The Interests of the Female Sex.”
    Paul graduated in 1841 and proudly displayed behind his name the initials G.B.M.C.—Graduate of Bengal Medical College. It announced his elite status, as did the Europeanizing of his surname.
    His big break came when he was transferred to Benares. For Hindus, it was the holiest city in India, located on the banks of the Ganges, the most sacred of rivers. His post gave him a commanding view of yogic life. Hundreds of temples lined the river, and pilgrims came from all over to bathe, or to cremate the bodies of loved ones, eager to wash away sins and win salvation. So, too, mystics flocked to the ghats, or wide stone steps, to take purifying dips in the river, to practice yoga, and to meditate. At least one slept on a bed of nails. The Buddha gave his first sermon nearby. For ages, Benares served as the heart of Hinduism, playing the same kind of role that Mecca does for Muslims and the Vatican for Roman Catholics. Many Hindus still consider it the holiest place on earth.
    Paul’s Treatise on the Yoga Philosophy appeared in 1851. London that year was holding its Great Exhibition. It was meant to draw attention to Britain as the leader of the industrialized world.
    The regimental surgeon seemed eager to show that the colonies, too, could participate in the march of progress.
    Paul commented on such things as the Aghori, the cannibal sect, noting the group’s heavy consumption of liquor. But his book generally ignored the remarkable diversity of Hindu mystics and instead zeroed in on their talent for life suspension or, as he put it in his preface, “abstaining from eating and breathing for a long time, and of becoming insensible to all external impressions.”
    His principal case study was the forty-day burial. The Punjab yogi’s triumph over death, Paul noted, “has puzzled a great many learned men of Europe.” But he—lowly Bengali surgeon that he was—would deign to enlighten his peers.
    Paul’s explanation had nothing to do with challenging poses or purifications. Nor did it deal with anatomy. Instead, he focused on an unseen factor that scientists of his day were busy measuring and evaluating in people and the environment.
    It was carbon dioxide,the waste product of cellular respiration that we all exhale. He had learned much about the basics of the transparent gas in medical school and quickly realized that yogic rituals worked to bottle it up inside the body. The main technique of manipulation was pranayama—the Sanskrit term for breathing exercises and, more literally, control of the life force. Prana means “vital force” and yama means “to restrain or control.”
    Paul gave many examples of how yogis manipulate their breathing to discharge less. For instance, he described a common practice in which yogis take fewer breaths. Such retention, he wrote, “has a remarkable effect” on reducing how much carbon dioxide a person exhales.
    His figures showed big drops over an extraordinary range of breathing rates, starting with the fastest. A relaxed person takes roughly fifteen breaths per minute. Paul’s findings showed that a yogi who took ninety-six breaths a minute would expel seventy-nine cubic inches of carbon dioxide. At