The Midnight Convention

A guild of merchants from different regions needed to set a standard measure for cloth. They couldn’t agree in their letters — each region had its own tradition.

But when they met, they discovered they had all brought cloth measured in the arm’s length of an average man. Not because it was the most precise unit, but because it was the one unit every culture independently found obvious.

The arm’s length was not scientifically optimal. But it was the measure that every merchant, in every region, expected every other merchant to recognize. Its universality made it the natural convergence point.