The unit Foot
Historically the "foot" was a part of many local systems of units, including the Greek, Roman, Chinese, French, and English systems. It varied in length from country to country, from city to city, and sometimes from trade to trade. Its length was usually between 250 mm and 335 mm and was generally, but not always, subdivided into 12 inches or 16 digits.
The United States is the only industrialized nation that uses the international foot and the survey foot (a customary unit of length) in preference to the meter in its commercial, engineering, and standards activities
The problem with this unit, is it different lengths in various parts of the word:¨
1 Russian foot (English foot, borrowed from Peter the Great) = 12 inches = 1/7 Russian sazhen = 0.3047 m.
1 French foot (pied du roi) = 12 pouces = 0.32484 m.
1 Amsterdam foot( voet) = 0.2831 m.
1 Rotterdam foot = 0.296 m.
1 Venetian foot = 0.34773 m.
1 Danish foot (after 1835) = 0.3138535 m.
1 Norwegian foot (after 1824) = 0.31375 m.
1 Swedish foot = 12 inches (tum) = 0.2969 m.
1 Portuguese foot = 0.3285 m.
1 Spanish foot (-1752) (Pie de Ribera/de Rey) = 12 Pulgadas = 0.287342 m.
1 Spanish foot (1752 -1765) (Pie de Burgos/Castellano) = 0.278635 m.
1 Spanish foot (1765-) (Pie de Rey) = 12 Pulgadas = 0.32483 m.
1 Greek foot - 0,3205 m (192,3 m = 600 Greek foot).
600 Greek feet was the lengths of the Olympic stadium (in Olympia: 192,3 m)
It makes the world a lot more easy when measurements is not a fixed units.
Countries which have officially adopted the metric system: The entire world, except:
Countries which have not officially adopted the metric system (United States, Burma and Liberia)
https://en.wikipedia.org/wiki/Metric_systemUmm nice liga: United States, Burma and Liberia