I generally measure things in attoparsecs, one of which is about the distance between the end of my thumb and its first knuckle. Femtoparsecs are useful for measuring car journeys.
Densities should always be quoted in international standard carats per cubic fathom.
I thought everyone knew that the speed of light is a foot per nanosecond to an adequate accuracy. It’s all you need to know if you want to make delay lines from optical fibre. Remind me someday, when you’re especially bored, to recount the time when I helped build a photon time-of-flight spectrometer. (It should be well known that the speed of light depends on wavelength ;-). The guy who designed and did >90% of the construction had a peer-reviewed paper published in a reputable journal.