Online
I ran across this on another forum I frequent and thought it interesting. John Harrison, the man who famously invented the marine chronometer for the purpose of determining longitude at sea, had the plans for this clock in a book he published a couple of years before his death. Martin Burgess, a British clockmaker, decided to build the clock and back in April Guinness certified it as "most accurate mechanical clock with a pendulum swinging in free air."
https://www.theguardian.com/science...n-harrison-vindicated-250-years-absurd-claims
https://www.theguardian.com/science...n-harrison-vindicated-250-years-absurd-claims