Deprivation ritual

A deprivation ritual was a form of meditation where a Jedi was suspended in a liquid tank with a slowly decreasing air supply, which allowed them to become one with the Force as much as possible without dying. Jedi Master Yoda underwent a deprivation ritual during the Clone Wars after he was contacted by the spirit of Qui-Gon Jinn. Undergoing the ritual, he made communed with Jinn once again, and was told to go to Dagobah.