Atlantis

"Legno santo," said Peter Schmidt, pointing to the glowing piece of charcoal. "Now, Frederick, you will get to see those antlike little elves that are called noctiluci or night-lights. They pompously call themselves Toilers of the Light. But whatever their name, it must be admitted that they are the ones that take the light hidden in the entrails of the earth, store it up, and sow it in fields, the soil of which has been especially prepared; and when it has grown to its full size and has borne fruit a hundredfold in the shape of gold sheaves or nuggets, they harvest it and save it for the darkest of dark times."

And, actually, looking through a crevice, Frederick saw something like another world, with a subterranean sun shining on it. A multitude of little elves, the Toilers of the Light, were mowing with scythes, cutting stalks, binding sheaves, loading carts, and storing in barns. Many cut the light out of the ground, like nuggets of gold. Undoubtedly it was the gold meant for the mint in Washington that was haunting Frederick's dreams.