By “two held out hands”, do you mean a person’s wingspan? Is there something similar for centimeters? I’m asking out of genuine curiosity and not antagonizing. I would love to have more tools at my disposal. An inch, for example, is the length of the first digit of the index finger. [0]
With length, I find that most of my use cases are division into equal parts as opposed to scaling. The imperial system was designed for this (frequently using base 12) [1]. I understand that this may be due to my framing.
I agree with the sibling comment about temperature granularity. Fahrenheit set 0 degrees to the coldest temperature in his hometown, then used freezing water and body temperature as reference points. 100 degrees is about body temperature, and around as hot as ambient temperature gets for many people.
[0] Useless trivia: an acre is one chain (66’) by one furlong (660’) and was supposed to be the amount a field a single ox could plow in a day. Neither of the latter two measures are commonly used anymore but a mile was redefined from 5000’ to 5280’ to make it an even 8 furlongs.
[1] Apparently this is the reason that the French failed twice to establish Metric Time
