[Nateman]

You could measure a person's volume by putting them in water and measuring the water displaced. Our total area , however, changes every time we move. That is why skin is flexible , so that it can stretch or shrink as we move.

Even if that were somehow possible to stadardize , calculating a person's area is not a trival problem. It is like measuring the length of a shoreline. The finer the detail you are willing to use the longer the total shoreline becomes. It is known as the Coastline Paradox

[Born in 1950]

We learned about putting a grain of wheat on a chessboard square and doubling it 63 times in the 6th grade. The dependence of a measurement on the measuring device used we were taught in the 7th.

Both non intuitive!

Remember this is not about measurement. No. Rather identification.

Good point though re skin's elasticity But that's merely an engineering problem. Spitballing it here.. Inflate subject, introduce subject into an air tight, pressure regulated room. Calculate based on the pressure differential with subject in versus subject out.

An advantage to this approach is you are using gas molecules as a measuring device.. can't get more “true” than that.