The Magnet by Leo Tolstoy

In olden days there was a shepherd whose name was Magnes. Magnes lost a sheep. He went to the mountains to find it. He came to a place where there were barren rocks. He walked over these rocks, and felt that his boots were sticking to them. He touched them with his hand, but they were dry and did not stick to his hand. He started to walk again, and again his boots stuck to the rocks. He sat down, took off one of his boots, took it into his hand, and touched the rocks with it.

Whenever he touched them with his skin, or with the sole of his boot, they did not stick; but when he touched them with the nails, they did stick.