Watch and learn the favorite exercise routine of early 20th century Europeans.

People often comment on my father's physique. Toned doesn't quite capture it: He looks carved. Unusually muscular. He is also, by any measure, ridiculously strong. He has never, to my knowledge, belonged to a gym. He plays tennis a bit. He skis (beautifully), but only once or twice a year. There was a short tenure as a coxswain; it ended when he smashed the boat.

For as long as I can remember, my father has maintained the same workout regimen. Most mornings, as the rest of the house struggles to start the day, he begins a series of exercises—the "Müller technique." Body swings. Stretches. Hopping on one foot. Lunges with arms windmilling, first backwards, then forwards. Sit-ups, push-ups, toe-touches. He does all this clothed in nothing but underwear. He is finished in 25 minutes, or less.

When I was very young, I remember watching my grandfather practice Müller as well, as he had each morning since he learned it at Jewish summer camp on the banks of Austria's Lake Wolfgangsee. After I gave birth and found it harder to get to the gym, my father suggested I try Müller: "You can do it at home!"

Born in Asserballe, Denmark in 1866, J.P. Müller was, for a time, as famous as that other Danish export, Hans Christian Anderson. Maybe more. At the turn of the last century, Müller's wildly popular cult of physical fitness swept Mitteleuropa, turning parlor-sitting dandies from Copenhagen to Berlin to London into ironmen. Müller's My System was published first in 1904 as little more than a long, bound pamphlet graced with an image of the Greek athlete Apoxyomenos naked and toweling himself. The exercise guide, which promised that just "15 minutes a day" of prescribed * exercise would make "weaklings" into strong men (and women), was ultimately translated into 25 languages, reprinted dozens of times, and sold briskly well into the 20^th century.

Müller was the Tom Paine of free body movement and fresh air. Like many a radical, he was resisted at first, called pornographic (partly because he often appeared in a loincloth—even while skiing in St. Moritz). His was a call to throw off the restrictive shackles of the Victorian era—a literal stripping away of restrictive layered clothes and corsets, a rejection of the "pallid, sickly looks" once prized as beautiful, and the "false dignity which forbids people, for instance, to indulge in so healthy and beneficial an exercise as running." He admonished: "Do not let a day pass without every muscle and every organ in your body being set in brisk motion." And bathing—the man had a fondness for cleanliness many of his contemporaries did not share: "This does not only refer only to people of the 'working' classes. I have often met 'gentlemen' in frock-coats and top hats and ladies in evening dress of whom you could tell by the smell of them, even at a distance of several feet, that they seldom or never took a bath."

Born sickly himself, so small "I could be placed in an ordinary cigar box," Müller nearly died of dysentery at two and "contracted every childhood complaint." His own strength, in other words, was acquired, not inherited, through physical exercise.

The Müller system is pretty much as I observed each morning growing up; it is something like a precursor to Pilates, it borrows from ballet, and it needs no equipment, other than commitment. It is strict but appealingly accessible. Unlike some of the other popular physical fitness gurus of the time—including the Prussian Eugene Sandow, who is known as the father of bodybuilding—Müller wasn't interested in building muscle mass through dumbbells. And while My System wasn't only aimed at men—in his original pamphlet, he explains that a woman needs to develop a "muscular corset" (that is, core muscles)—Müller, eventually, added to his bookshelf, writing My System for Ladies and My System for Children. There was also the remedial My Breathing System for those for whom, trapped in a Victorian sartorial nightmare, respiration had to be taught.

Aside from being popular, My System was also intuitively, precociously, on the mark. In an age of rampant tuberculosis infection, Müller insisted practitioners must both open windows and allow the sun to touch the skin. (At the time he published My System, Müller was working as an inspector at the Vejlefjord Sanitorium for Consumption.) This advice was, as Dr. Lee B. Reichman wrote in 2003's Timebomb, among the few TB-preventative options available in the preantibiotic era. Müller also recommended common-sense daily living: eating and drinking alcohol "in moderation," getting eight hours of sleep, drinking water, caring for your teeth, giving up the pipe.

Best of all, My System is open to all. Where many of the other gymnastics movements—and there were dozens upon dozens of others born in Europe around the same time—had aggressively nationalist, proto-fascist, and often anti-Semitic overtones, Müller was refreshingly secular and remarkably nonideological. Müller's system could be enthusiastically embraced by Jew and gentile alike. That is probably what appealed to his most famous devotee, Kafka.

Franz Kafka was a fanatical Müller follower. He would do the movements, fully naked, in his window, twice each day, whirling his arms and twisting this way and that, practicing the same hops and isolations advocated with similar vigor by my family. Indeed, My System became an integral piece of Kafka's obsession with the body. When Müller's women's pamphlet was published, in 1913, Kafka sent a copy to his fiancée, Felice Bauer, recommending she pick up a daily practice as well. "If they bore you, it shows you are not doing them properly," he wrote.