Stone Crypt (MK20)

KOAN:

You go to visit a family crypt. It is a stone mausoleum in the cemetery. You go at night when there is no moon. You decide to open the gate and go in to be nearer your ancestors. It is pitch black. A fierce gust of wind blows your candle out and you hear the heavy gate slam shut behind you. There is no one around. There are no windows and the door is locked from the outside—how will you get out?

—PZI Miscellaneous Koans, Case 20

Short version: You find yourself in a stone crypt. There are no windows and the door is locked from the outside. How will you get out?