Take a well and cook it. What do you mean, one pot of water gets five barrels of salt?

The ancients directly used the natural gas generated underground as the raw material for cooking salt, and boiled a pot of water to get five buckets of salt. Cooking with well fire means taking underground natural gas as fire, and a pot of water means taking five pots of water and getting five barrels of salt, so cooking with well fire and getting five barrels of salt means that the ancients directly used underground natural gas as raw material to cook salt and boiled a pot of water and got five barrels of salt.