ONE by one, the trapeze artists topped off their routines by dropping from their high-swinging bars into the net stretched below, then rebounding into somersaults — to the roar of the crowd at the travelling circus in Cedar Rapids, Iowa.
And one child in the stands began to wonder: Hey, what if there was a contraption that made it possible to keep on bouncing and flipping?
George Nissen, then 16, who was a member of the gymnastics and diving teams at his high school, was soon tinkering in his parents' garage, strapping together a rectangular steel frame and a canvas sheet. Even though it was not quite as springy as he had hoped, he called it a bouncing rig. That was in 1930.
It would be several years later, while he was a business major at the University of Iowa, that Nissen and his gymnastics coach, Larry Griswold, would work together to make a more flexible contraption with a nylon sheet.
They still called it a bouncing rig.
Then, in 1937, Nissen and two of his friends formed a travelling acrobatics act called the Three Leonardos and began performing throughout the Midwest and Texas and then in Mexico. It was while they were there that he heard the Spanish word for diving board: el trampolin.
He added an "e" and registered "Trampoline" as a trademark for what has become a joy-inducing device for backyard tumblers, fitness freaks and, since 2000, Olympic athletes.
Nissen devoted his life to promoting and manufacturing the trampoline and once went to the length of renting a kangaroo to bounce with him in New York's Central Park.
Dwight Normile, the editor of International Gymnast magazine, said of Nissen: "He took the device all over the world and gave them as gifts.
"He wanted everybody to know about the health benefits of bouncing on a trampoline."
Ten years ago, Nissen spoke of his enduring goal to see trampolining become an Olympic sport.
For years, his friends had told him he was just dreaming.
"They said, 'George, it will be the year 2000 before trampoline is ever in the Olympics'," Nissen said in an interview with International Gymnast.
They were right. "He was at those Sydney Olympics in 2000, 86 years old at the time," Mr Normile said, "and they actually invited him to bounce on the official trampoline."
A twist was that in the early 1950s, Nissen had donated a trampoline to the Soviet Union – its first. And it was Russia that won the first Olympic gold medals for trampolining in 2000.
George Peter Nissen was one of four children born to Franklin and Catherine Jensen Nissen. His father owned a dry goods store. The family later moved to Cedar Rapids.
George started tumbling when he was a child at a local YMCA and continued in junior high and high school.
At the University of Iowa, he was a three-times winner of the intercollegiate national gymnastics championship.
After making the first prototype trampoline, Nissen and Mr Griswold, his college coach, opened a small factory in Cedar Rapids and began marketing the device.
However, initial sales were slow, and Mr Griswold, who died in 1996, went out on tour as a comedic acrobat under the name the Diving Fool.
Nissen, meanwhile, continued to make and market trampolines, even persuading the military to buy them as a training tool for pilots and divers.
He served in the Navy during the Second World War, then returned to Cedar Rapids to expand his company. The Nissen Corporation, which he sold in 1973, eventually produced a full range of gymnastics equipment.
In 1951, Nissen married Annie De Vries, a high-wire artist from the Netherlands who was performing with the Cole Brothers Circus in the United States.
Well into his later years, Nissen remained head over heels in love with his sport. In 1977, with his son-in-law Ron, he scaled a pyramid in Egypt – one with a flattened top – set up a trampoline and did some flips.
Year after year, he also attended the National Collegiate Athletic Association gymnastics championships in the US.
"And at the banquet before the competition, he would do a handstand," Mr Normile said. "It became a tradition.
"The last time I saw him there was in 2006. He did one of those kind of yoga headstands where you're on your head and elbows. That was only four years ago; he was 92."
Besides his wife Annie, Nissen is survived by his two daughters, Dagmar and Dian , and one grandchild.