Hans Zinsser, Rats, Lice and History
(New York: Bantam Books, 1971), p. 137:
Lice have even been important in politics. Cowan tells the story of the custom prevailing in Hurdenburg in Sweden, where in the Middle Ages a mayor was elected in the following manner. The persons eligible sat around a table, with their heads bowed forward, allowing their beards to rest on the table. A louse was then put in the middle of the table. The one into whose beard the louse first adventured was the mayor for the ensuing year.