Hole to "China"

When I was a young boy, I used to play around the farm, but there was one room that I was forbidden to go into: the entrance to the granary barn. Anytime I ever stepped over the threshold to enter, I'd hear a voice warning me, "Do not come in here, there is a deep, deep hole, and you'll fall all the way down and into China." It was only later on in life that I discovered it was just to keep me out of the building so he could get on with work. It just so happened that this hole was not the depth of the earth, but in fact only the depth of my boots.