The word 'salary', which designates remuneration for work, has a very specific origin in Ancient Rome. To what basic product is it etymologically linked?

The word 'salary' comes from the Latin 'salarium', which in turn derives from 'sal' (salt). In Ancient Rome, soldiers were sometimes paid with a ration of salt ('salarium argentum'), a very valuable product at that time for preserving food. It is also said that this salt was used to pay the workers who built the Vía Salaria, the route by which the salt was transported. Hence today 'earning a salary' means receiving payment for work.