Whenever we measure something, it is usually inexact. For example, the mass of a baseball will never be measured exactly on a scale in any unit of measurement besides "mass in baseballs that are currently being measured" and rational multiples thereof.
Are there any non-arbitrary physical quantities that are "inherently" rational? That is, quantities that can be expressed "exactly" in a non-trivial, fundamental unit of measurement?
As far as I know, there is total charge, because charge can always be represented as an integer multiple of the charge of an electron. And to an extent, photons/light can be described this way too. Are there any others?
Also, are there any inherently "algebraic" quantities that are not inherently rational? That is, quantities that can be expressed closed-form as the solution to an algebraic equation in a non-trivial unit of measurement, but not as an "exact" ratio to that unit of measurement?