Pluto is not only ruler of the Underground, but also the symbol of abundance and wealth. It is symbolized also by "the Pearl of great price" which, hidden within the viscous shell-enclosed substance of the oyster, can only be found by the daring diver into the sea-depths of the unconscious; and, in order to succeed in his quest, the diver must develop a large lung-capacity for breathing — the breath symbolizing the most essential aspect of the process of spiritual realization.
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