Nicotine

The magician borrows a bill from a spectator who signs it for later identification. He puts the bill in an envelope and takes a cigarette box out from his pocket. He asks the spectator to choose a cigarette from the box, writes the spectators initials on it, and puts it into the envelope as well, which he then seals. The magician then uses his lighter and sets fire to the envelope, burning it and the enclosed bill and cigarette to ashes. The magician picks up the marker, removes its lid and shows that the signed cigarette has mysteriously appeared inside! He breaks the cigarette in half and shows that there is a rolled-up bill inside! Thespectator himself removes the bill and amazingly discovers that it's his signed bill!