At 02:41 PM 6/29/2012, Scott Daniel - Turbovans wrote:
>Where did they derive that dimension from ?

As Mike said...but the actual definition from 1889 to 1960 was the
distance between two scribed lines on a platinum-iridium bar kept at
the International Bureau of Weights and Measures in France, measured
at the melting point of ice.  In 1960 it was redefined in terms of
the wavelength of a particular emission line in the spectrum of
krypton-86, and in 1983 redefined once again as the distance light
travels in vacuum in a specific time (roughly one three hundred
millionth of a second).

Here's a photo of the working end of one of the original prototype
metre bars, specifically the one that was the US National standard
for the meter until 1960. http://museum.nist.gov/object.asp?ObjID=37

Yours,
David