An elderly Polish woman who lived in a rural part of Poland where there were no doctors told me this.
The sufferer (usually a teenager) sits at a table. On the wall is a large mirror. A folded bath towel soaked in water is placed on the subjects head. A pile of straw is placed on the towel. A bowl of water in which a piece of charcoal is floating is placed on the table in front of them and they are told to gaze at it until the charcoal sinks.
The straw is then set alight.
Cute, eh?