The subtle body of the yogi, when liberated, visits different planes of existence. Flights into space and descents into the depths of the planet are equally possible. A study of planetary cataclysms will provide an understanding of the stratifications of life. It can be observed how animals became fossilized when caught in a mineral flow. When moving through the subterranean channels, the yogi can see to what extent the foundations of our planet have become worn out. Thus the spirit of the yogi becomes familiar with the conditions of ancient formations, and afterward nothing can appear to him as stable or complete. Such a realization is needed for the progress of the spirit. A striving toward perfection will come through an understanding of imperfection. (AY (opens in new tab), 224)