There was a man in the 1920s named Edward Leedskalnin, and he built a small castle made of 3 million pounds of coral rock. Some of the coral stones that he built it with weigh 30 tons. The tools that he had were only simple pulleys and winches and chains. Scientists do not know how he did it. The equipment he had was not strong enough to lift the great stones. He said that he knew the secret of how the Egyptian pyramids were built. He did his own experiments on magnetism and developed his own theories. People spying on him with binoculars swore that they saw the great stones float in the air; they signed sworn affidavits. It seems like he knew some secret of using magnetic force to make the stones weigh less.