From Muladhar down to the sole of the foot is called the physical plane. Below is the domain of subconscience.
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There are many planes above and below. But mainly there are four planes below. They are the mental, the psychic, the vital and the physical. And above there are many planes, the Supermind and Sachchidananda being the highest.
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If it happens that you go down at all, bring down there the Mother’s light and power by your aspiration. Establish the kingdom of the Mother below as it is above.
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When the consciousness descends into the physical, it does not mean that the results of all sadhana have gone, they really remain behind the veil. One has to bring down the consciousness, the light and the power of the Mother into the obscure physical. When these are established the former state will not recur. But if you are perturbed, depressed and think that nothing can be done in this life and that to die is preferable and so on, then it becomes an obstacle for the consciousness, the power and the light to descend. That is why these wrong feelings have to be rejected and you should depend on the Mother and silently aspire to Her.
About Savitri | B1C3-08 The New Life (pp.28-29)