Ein Seismograf natürlich. ;-) Um das Zitat unten abzukürzen: spätestens wenn jedes Fröschlein einen Ball abbekommen hat ist es Zeit in den Keller zu gehen.

The Chinese philosopher Zhang Hêng invented the earliest known seismoscope in 132 A.D. The instrument was said to resemble a wine jar of diameter six feet. On the outside of the vessel there were eight dragon-heads, facing the eight principal directions of the compass. Below each of the dragon-heads was a toad, with its mouth opened toward the dragon. The mouth of each dragon held a ball. At the occurrence of an earthquake, one of the eight dragon-mouths would release a ball into the open mouth of the toad situated below. The direction of the shaking determined which of the dragons released its ball. The instrument is reported to have detected a four-hundred-mile distant earthquake which was not felt at the location of the seismoscope.

Scientists Resurrect World’s Earliest Seismograph via the nonist