According to the present definition, hardness is the resistance a solid body sets against the intrusion of another, harder matter.
Die Hardness measurement is a relatively old method and has been in the course of time continually further developed and improved. The following table gives an overview of the development:

Time	Description
1640	Barba: evaluates the hardness of precious stones by means of a file
1722	Reaumur: determines the hardness of steel by scratching with various minerals develops an indentation method with two triangular prisms of the same material pressed crosswise one on the other
1801	Hauy: System of scratch hardness with 4 hardness steps
1820	Mohs establishes a scratch hardness scale encompassing 10 hardness steps
1874	Uchatius: evaluates the hardness of bronze by means of a chisel falling down from a height of 25 cm (dynamic hardness measuring method)
1900	Brinell: develops the ball indentation test named after him
ca. 1905	Martens: develops the indentation principle of simultaneous measurement of test force and indentation depth
1907	Shore: Rebound hardness measuring method for steels
1920	Rockwell: Hardness measuring method with preliminary test force and depth measurement
1925	Smith und Sandland develop the Vickers hardness measuring method