divining rod

noun1

1. •
   Rod used for dowsing, a technique of divination used to locate subterranean sources of water, metal, other mineral resources or even various other things through magic, or according to many believers a natural phenomenon.

   • Dan produced his divining rod - a piece of forked willow tree - and taking a firm grip of it with both hands, went off ‘merry-widowing’ round Skinnerlouse’s yard. — 1911