The unit of measurement ‘the yard’ has been in English usage for hundreds of years. Quite how it’s length came to be a unit of measurement is lost but various theories abound, it roughly equates to a man’s stride or it has been suggested that it is the girth of a man.
The need to standardize measurements became more and more critical as engineering and building gathered pace in the C18th. Various attempts had been made at defining it but eventually the Royal Society were tasked with the job and in 1814, John Playfair, Hyde Wollaston and John Warner proposed defining it on the basis of the length of a pendulum with a period of one second, placed in Greenwich. The said pendulum would be kept in a vacuum, at sea level, at Greenwich.
Parliament finally enacted it in 1824, ten years after it had been proposed.
The yard then measured 39.1392 inches.
This then gave way to the Imperial Standard Yard of 1878