CodyDon Reeder carefully filled a tub full of mercury and then set a heavy iron anvil on top. Despite the anvil’s substantial weight, it floated easily above the shimmering liquid. Reeder even tried to sink the anvil, but it just kept popping up again. This is due to the varying density between the two metals.
The iron anvil floats because mercury has a density nearly twice that of iron. In fact, due to the density ratios, the iron actually floats better than wood does in water.