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Leonardo, about 1490. The oldest famous drawing of a human as a unit of measure.
Roughly the middle of this drawing: 26 powers of ten separate you from the observable universe, and about 35 separate you from the Planck length.
It is the one scale where the units were not invented for the object. The object came first.
Skin in cross section: layers, a hair, a gland, and the nerves that report on all of it. The last level you can see without help, and only just.