What is chronometer? Less casual than chronometer?

What is the moment when you realise you have a lot of patience to master a task of all the elements? ”

tun (plural tuns)

1. A large cask; an oblong vessel bulging in the middle, like a pipe or puncheon, and girt with hoops; or a fire cask.
2. (brewing) A fermenting vat.
3. An old English measure of capacity for liquids, containing 252 wine gallons; equal to 2 pipes. (Not modern)

“Toon” formally became the more often seen “ton”, but has a more representative connotation of water itself as opposed to volume or weight measurement, paralleling your use of “thimble”