Metamorphosis is the name of a stage illusion invented by John Nevil Maskelyne, but most often associated with famous escape artist Harry Houdini and performed to some renown (for speed) by The Pendragons, among others.
In the illusion, an assistant (Houdini employed his wife Bess) is locked inside a large box or trunk, often after being restrained with handcuffs, ropes, bags, etc.
Variations include the Aquarian Illusion created in the 1970s by Alan Wakeling for Mark Wilson, who performed it in The Magic Circus series and a HBO special Mumbo Jumbo!
Penn and Teller performed the illusion in an underwater theatre with a female assistant (a Weeki Wachee "mermaid") handcuffed and locked in a steel cage on the sea bottom.
Many of today's leading Illusionists around the world buy the rights off John Taylor to be able to perform his original invention Suspended Animation.