Of course determining Longitude requires precise knowledge of the time.
And that prompted the English Parilament to offer the "Longitude Prize" in 1714.
The prize was £20,000, (equivalent of £2 million today).
So John Harrison set to work creating a timepiece that would keep accurate time on board a pitching ship.
His first three models (Called "H1, "H2", and "H3") were large brass contraptions.
They sent H3 out on a trial voyage, but they had no way of determining the accuracy of H3.
So Harrison developed "H4" which was a pocket-watch and turned out to be better than H3.
It rather reminded me of the volt-nuts here on these forums and the issue of how do you measure things.
A photo of H1, H2, H3, H4, and H5