What is the Gram ?

Source: en.wikipedia.org

" The gram (originally gramme; SI unit symbol g) is a unit of mass in the metric system.
Originally defined as of 1795 as "the absolute weight of a volume of pure water equal to the cube of the hundredth part of a metre [1 cm³], and at the temperature of melting ice", the defining temperature (~0 °C) was later changed to 4 °C, the temperature of maximum density of water.
However, by the late 19th century (...) "