The Absurdity of English Units
I think it speaks for itself; some of these are now historical.
Just remember how hard it is to say millimeter and kilometer, before proceeding:
English units
unit  equal to 

poppyseed  ¼ barleycorn 
barleycorn  ⅓ inch, the length of The Standard Barleycorn^{1} 
inch  3 barleycorns (yup) 
nail  2¼ inches 
hand  4 inches 
link  7.92 inches [sic] 
foot  12 inches, feet that fit size 14 shoes 
yard  3 feet 
fathom  6 feet 
rod  ¼ chain, 16½ feet 
chain  22 yards, 100 links 
skein  360 feet 
furlong  220 yards, 10 chains 
mile  80 chains, 5,280 feet 
league  3 miles 
You can’t make this stuff up. Well, it seems like you can. It seems like somebody did, slowly, via committee.
A subset of these became standardized as the Imperial Units, which included Just 8 Convenient Units for describing length (bolded above). It cut down on about half the nonsense, but it’s still kinda crazy why we need so many units when we have place value numerals & SI prefixes for orders of magnitude.
But like the quote the future is here, it’s just not evenly distributed, most of these units are dead to most of us, who understand only feet & inches (probably to measure ourselves), yards (because of football), and miles (because of cars).
Let’s just use metric
Seriously.

I doubt there actually was such a thing. But it would be funny to imagine a single kernel, under glass, under glass. But seriously, the barleycorn was the base unit ↩