This was particularly interesting. This is how Ruslan's grandfather's household "purified water" - This particular stone has been hollowed out to a kind of funnel shape. Water is poured into the stone and then it filters through the stone and is collected in the milk can down below. In the next two pictures you see the end product and the two buckets of the "before" filtration product. I didn't drink the filtered water myself, but all the family members would dip in and get clean water. I would drink it if it was boiled. Quite a clever and remarkable system.