Throughout history, the search for salt has played an important role in society.
Where there was no salt near, it was brought from great distances. Thus, salt became one of the most important articles of early trade. Records show that in areas of scarcity, salt was traded ounce for ounce for gold. Rome's major highway was called the Via Salaria, that is, the Salt Road. Along that road, Roman soldiers transported salt crystals from the salt flats at Ostia up the Tiber River. In return, they received a salarium which was literally money paid to soldiers to buy salt. The old saying "worth their salt", which means to be valuable, derives from the custom of payment during the Empire. The caravan trade of the Sahara was also primarily an exchange of goods for salt. Among ancient peoples there, to eat salt with another person was an act of friendship. Slaves were often purchased with salt. Salt was so important in the Middle Ages that governments retained salt trade as a monopoly, or levied taxes on its purchase. By then, people's social rank was demonstrated by where they sat at the table, above or below the salt.
Even today, in some remote regions of the world, salt is a luxury item. In fact, in a few isolated areas of Southeast Asia and Africa, cakes made of salt are still used for money.