Radiesthesia
Radiesthesia (Latin radius + Greek aisthesis) is the alleged faculty of perceiving "radiations" emitted by objects, people, places — through tools like the pendulum or the dowsing rod. Dowsing for water is the most popular application, present in many rural cultures.
Scientific status
Controlled double-blind tests (Munich, 1986-87, with 500 dowsers) showed results equivalent to chance. The detected movement is the ideomotor effect, not perception of "radiation".