A divining rod is geological you say?!?! Now hear me out.
A "divining rod" is a "magical" stick, often in the shape of an "L", that helps the user find various things under the ground's surface including (most commonly) water, but also oil, gold, gems, etc. It is considered a "pseudoscience", since it doesn't involve an evidence based system of determination and instead uses the user's "feelings" to determine where to find what they are looking for.
Even though the divining rod is basically guesswork at it's most glorified, it could be considered the first step along a long road for humanity to determine how to accurately and repeatedly find the location of valuable underground commodities, such as water and petroleum. It is a first step to the scientific method for exploration (try, repeat, doesn't work, move on to a new method).