Thoreau writes in his journal:
By taking the ether the other day I was convinced how far asunder a man could be separated from his senses. You are told that it will make you unconscious, but no one can imagine what it is to be unconscious—how far removed from the state of consciousness and all that we call “this world”—until he has experienced it. The value of the experiment is that it does give you experience of an interval as between one life and another,—a greater space than you ever travelled. You are a sane mind without organs,—groping for organs,—which if it did not soon recover its old senses would get new ones. You expand like a seed in the ground. You exist in your roots, like a tree in the winter. If you have an inclination to travel, take the ether; you go beyond the furthest star.