It wasn't until that evening, when we sat in a windowless break room drinking terrible coffee, that he revealed why he'd kept showing me magic tricks—to refute, in a way, Arthur C. Clarke's famous dictum, that advanced technology is "indistinguishable from magic." First, though, Cohn set aside his coffee and cracked his knuckles. "Now," he said in a P.T. Barnum voice, "I'll show you the amazing disappearing saltshaker. Usually I do this with a special silk, but . . ." He looked around, grabbed a stiff brown paper towel, shrugged, and wrapped the plastic shaker in it. "No, wait," he said, the smoothness of his act ruined. "This is the amazing saltshaker-through-the-table." He set the wrapped saltshaker down on the table with a loud clunk, stopped, took it away, and said, "Sorry. Maybe it'll work better with these." He put some packets of pepper on the table, thought a second, and then swept them away. Something had him rattled, I couldn't tell what. "No, it's the saltshaker. That's right." He set it up on the table again with one hand and smacked it hard with his palm. The paper towel flattened out, and we heard the saltshaker bounce off the floor below the table. I bent to retrieve it, flummoxed.