[mbrubeck]

units.txt defines `water` like this:

    water := gram / cm^3     // Standard density of water (defined)

1 g/cm^3 is the maximum density of water at standard pressure (1 atm), which it reaches at 3.98°C.

(Or at least, that used to be true by definition. Using the current definition of the kilogram, and the latest measurements of water density, the maximum density is actually closer to 0.99997 g/cm^3.)

[nkrisc]

I see, that makes sense now.