What are life-preserving coffins?

Very much a historical oddity, the life-preserving coffin was a special burial casket designed by Christian Henry Eisenbrandt in 1843 to allow those mistakenly buried alive to safely get out. The system works by fitting the typical hinged lid with a series of levers and springs, which activate via motion-detecting devices in the coffin, ultimately releasing the latch. Any motion is detected through two mechanisms: a ring slipped around the occupant’s finger and a metal head plate. Both are connected by wires to the coffin’s opening mechanism, with the slightest movement triggering the lid catch. In addition to the opening mechanism, the life-preserving coffin also features a mesh in its lid which would supposedly provide a limited supply of air post-burial.