In 1983 I took a camel trip between Jaisalmer and Bikaner in Rajasthan and was led by a charismatic Pakistani. He had a wicked sense of humour and brought me to a waterhole where we were to eat. The water was full of life and caused me considerable concern.
My friend laughed - then proceeded to filter it through his turban. I was grateful to lose the insects, but not at all comfortable at the thought of what was being added to the water by the turban.
Was it an example of good local practice passed down through generations proving to be good science as well?