What makes Agricola valuable to a reference work on esoteric tradition is that he wrote down what the miners believed and then said what he thought of it, keeping the two clearly apart. He records the divining rod, the forked hazel twig cut and held in a particular grip so that it dips over a hidden lode, describes the ritual and the words used with it, and then reports the objection that a rod turns in the hands of a believer and does nothing in the hands of a sceptic, concluding that a prospector should rely on the visible signs of mineralisation instead. He records the underground spirits, the small figures in miners' dress that were said to appear in the workings, some helpful and some malicious, and treats them as part of the life of the mines rather than as demons requiring exorcism or as nonsense requiring suppression. He was also openly sceptical of the transmutation claims circulating in his own century, on the practical ground that he had never met anyone enriched by them. The result is one of the best sixteenth-century records of working folk belief, made by someone who did not share it, and modern histories of dowsing and of mining folklore rely on him heavily for exactly that reason.