Salt was used as means of payment in some form or other on all continents at some time. The "white Gold" was traded in the form of bars, slabs or other shapes, which was possible thanks to the dryness of Central Africa. The oldest reference to the use of bars of salt as money goes back to the Greek traveller Cosmas, who travelled through the empire of the Axumites, today's Ethiopia, in the year 525 BC. Although usually very durable, the rainy season could become a problem for the circulation of salt money. Badly stored salt would then dissolve in no time. Incidentally, in peasant dwellings salt had to be stocked out of the reach of cattle, or else it would be eaten.