Planck mass

unit of mass in the system of Planck units

The Planck mass is a small unit of mass used in physics. It is derived using an equation involving Planck's constant, the speed of light in a vacuum, and the gravitational constant. It is approximately 21.76 µg, which is a few times less than the mass of a human eyelash.

The idea was to have a definition based only on fundamental universal constants.