REFRIGERATE FOODS WITHOUT USING ELECTRICITY

This mode of refrigeration goes back at least 5000 years.
It uses a porous outer earthenware pot, lined with wet sand, contains an inner pot (which can be glazed to prevent penetration by the liquid) within which the food is placed - the evaporation of the outer liquid draws heat from the inner pot. The device can be used to cool any substance.
Have any of you tried this?
More info - http://en.wikipedia.org/wiki/Pot-in-pot_refrigerator