In antiquity, "systems of measurement" were defined locally: the different units might be defined independently according to the length of a king's thumb or the size of his foot, the length of stride, the length of arm, or maybe the weight of water in a keg of specific size, perhaps itself defined in "hands" and "knuckles". The unifying characteristic is that there was some definition based on some standard. Eventually "cubits" and "strides" gave way to "customary units" to meet the needs of merchants and scientists.