A mass may be measured by a scale with a fulcrum, such as this:

If the mass of *M _{1}* is a standard mass such as a kilogram, then the mass of

*M*can be determined from the law of the lever as follows:

_{2}*M _{2}* =

*M*×

_{1}*a*÷

*b*.

Such a scale can also be used to measure the inverse mass, 1/*M _{2}*, which I’m calling the

*vass*,

*N*:

_{2}*N _{2}* = 1/

*M*=

_{2}*b*÷ (

*M*×

_{1}*a*) =

*N*×

_{1}*b*÷

*a*.

The mass and the vass are related properties of a physical body. They can be measured together.