John Harrison, one of the world's greatest clockmakers, claimed to have designed the perfect pendulum clock in the mid-18th century. Instead of being celebrated, Harrison's plans were chastised and ridiculed by his peers. A clock that was accurate to within a second over a 100-day period was unheard of, and a mechanical clock that precise wouldn't be developed until the 20th century. But after a 100-day trial at the Royal Observatory in Greenwich, Clock B as it's known — which was recently constructed to Harrison's specifications — has vindicated Harrison, set a Guinness World Record, and shocked the horological world, according to The Guardian.

Nobody believed Harrison

"It is important to realize [Harrison's] design goes against everything the establishment has claimed is the best throughout history," Jonathan Betts, a senior horology specialist at the Royal Observatory told The Independent. In 1737, Harrison — a self-taught clockmaker — invented the marine chronometer, which revolutionized long-distance sea travel during a time when the developed world was rapidly becoming a larger place. But despite his accomplishments, Harrison's declaration about Clock B's accuracy was so far ahead of any clock during that time it was considered "an incoherence and absurdity that was little short of the symptoms of insanity" by the London Review of English and Foreign literature.

Our 100 day trail of 'Clock B' won @GWR for 'most accurate mechanical clock with a pendulum swinging in free air'! pic.twitter.com/m3pnorYlOz — Nat. Maritime Museum (@NMMGreenwich) April 18, 2015

"It was a claim that Harrison made and a claim nobody believed because the best clocks of the day couldn’t do better than about a second a week, if they were lucky," Betts told The Independent. "It was only in the 20th century that people thought that Harrison may have been right." Martin Burgess, a master clockmaker, used Harrison's mechanism and design along with modern materials like duralumin to construct the Martin Burgess Clock B, which has been sealed in a Perspex case at the Royal Observatory since January. In the 100 days since it was sealed, Clock B has only lost five-eighths of a second, setting a Guinness World Record for "most accurate mechanical clock with a pendulum swinging in free air."

Harrison's accomplishment, designing a clock in the 18th century whose accuracy hasn't been surpassed by the thousands of watchmakers who followed him, is truly remarkable and cannot be understated. Clock B even went against conventional clockmaking wisdom. A heavy pendulum bob and a short swing was thought to keep the most accurate time, but Harrison's design uses a wide swing and a lighter bob. It's akin to someone building the world's fastest car in 1940 with a diesel engine, and still holding the record for top speed today.

Despite its considerable accomplishments, the Royal Observatory's curator of horology, Rory McEvoy, told The Independent that Clock B could be even more accurate. "What we’ve seen here is something approaching a perfect clock, but we’re not there yet. We know we can adjust it to make it even better."