The word “salary” stems from the Latin word “salarium,” meaning “salt money.” The Romans paid soldiers, officers, and civil administrators an allowance of salt, and “salarium” came to be a term for military pay after salt was no longer used to pay soldiers.
Marco Polo in The Travels of Marco Polo, writing at the end of the 13th century, tells of Chinese salt money in the province of Kain-Du. In the words of Polo:
In this country there are salt springs, from which they manufacture salt by boiling it in small pans. When the water is boiled for an hour, it becomes a kind of paste, which is formed into cakes of the value of two pence each. These, which are flat on the lower, and convex on the upper side, are placed upon hot tiles, near a fire, in order to dry and harden. On this latter species of money the stamp of the grand khan is impressed, and it cannot be prepared by any other than his own officers. Eighty of the cakes are made to pass for a saggio of gold. But when these cakes are carried by traders amongst the inhabitants of the mountains, and other parts little frequented, they obtain a saggio of gold for sixty, fifty, or even forty of the salt cakes, in proportion as they find the natives less civilized. (Polo, 1958, 187)
Ethiopia offers the most recent example  of a society circulating salt as money, a practice that lasted into the 20th century in remote areas. As early as the 16th century, visiting European explorers noted the use of salt as money. Bars of salt money were called “amole,” after the Amole tribe that first introduced salt money to the Ethiopians. The bars of rock salt bore a marked resemblance to a whetstone, 10 to 12 inches in length, 1.5 inches thick, and black in color, perhaps from handling. They weighed about a pound. Referring to a millionaire, Ethiopians say “he eateth salt.” During the 19th century, Richard Burton visited Harar and observed that a slave cost a donkey-load of salt bars.
20th-century reports on the value of salt bars varied, some putting the exchange rate of salt bars at less than seven bars per dollar, and others reporting as many as 48 bars per dollar. In some areas, the bars could be broken up for small change, and Ethiopians enjoyed a reputation for accurately gauging the amount to break off.
The Ethiopians are known for having a strong attraction to the taste of salt, but the black bars were not used for consumption. White salt of a finer quality met the needs for seasoning, and the black bars were reserved for monetary uses. The use of salt as money gives added meaning to the phrase “worth his salt.” In virtually every quarter of the globe examples can be found of salt circulating as money at some point in history. It is one of those commodities universally in demand. Following the inflationary chaos of the Bolshevik Revolution, salt was the main standard of value, medium of exchange, and store of value in Moscow. 
Einzig, Paul. 1966. Primitive Money. 
Polo, Marco. 1958. The Travels of Marco Polo.
Williams, Jonathan, ed. 1997. Money: A History.