In 1920s Gyeongseong, a fraud built on the claim that mercury could be converted into gold drew substantial investment. Newspapers of the day covered the case at length more than once.

The losses were considerable in the currency of the time, estimated at the equivalent of some 15 billion won today. Investors included merchants and landowners as well as officials.

Why people believed it

Scientific findings about elemental transformation were then appearing in the newspapers. With radioactive decay newly understood, the idea that one element could become another was accepted as fact.

That is where the scheme drew its plausibility. Rather than inventing something wholly fictitious, it borrowed a fragment of a real scientific concept and attached to it a process no one could verify.

A recurring structure

Similar cases appear whenever new technical vocabulary spreads through the public. From electricity to radio to nuclear power and, lately, artificial intelligence, only the terms change; the structure is much the same.

Three features recur: a core process that cannot be checked, a promise of high returns to early participants, and pressure that the opportunity is about to close.

The principal in the Gyeongseong case was eventually arrested, though little money was recovered. A century-old record still repays reading less for its strangeness than because its structure still works.