They went to dig the soil at the base of the cliff wall, first excavating a small amount of shallow soil, placing it in a basin, then adding plenty of water, stirring it to dissolve the salt, and then pouring the murky solution into a pipe stuffed with dry grass.
The pipe was ten centimeters in diameter, two feet long, and two centimeters thick, and was somewhat heavy. Inside, there were grid structures that supported the dry grass.
The muddy water, filtered through the dense dry grass, turned into relatively clean brine, which dripped into the basin below.
Once everything was thoroughly filtered, they skimmed off the surface impurities and then placed the basin over a fire to boil.
As the water gradually evaporated, table salt began to crystallize out.
Once they saw minerals different from salt precipitating out, they stopped the fire and poured the remaining brine into a small pot to continue boiling, for the production of sodium nitrate.
