|≈||approximately equal to|
|digits||indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …)|
The Mark (from Middle High German: Marc, march, brand) is originally a medieval weight or mass unit, which supplanted the pound weight as a precious metals and coinage weight from the 11th century.
A grain is a unit of measurement of mass, and, for the troy grain, equal to exactly 64.79891 milligrams. It is nominally based upon the mass of a single seed of a cereal.