I want to know the answer to the following question:
What was exchanged from mouth to mouth in the usage of the seismometer?
All the background I'm provided with is that "This employed an inverted pendulum that, when disturbed by ground tremors, would trigger a set of gears that dropped a metal ball from one of eight dragon mouths (representing all eight directions) into a metal toad's mouth.". Is that enough to answer the question?