Maharshi Patanjali mentioned about a state of absorption of the mind with a thought called Savitarka. In the next level with intensity of practice comes the Nirvitarka Samadhi or absorption of the mind completely where the outer form vanishes and the essential reality alone remains in the form of a knowledge or awareness. Suppose the person is meditating on Om, in the earlier state, there is a name and form that is present in meditation. In a deeper level, the name and form dissolves and only the essence of Om exists in the mind as an inner light or a glowing experience.
With different efforts in Yoga Sadhana, the mind is purified and memory is cleansed. In this state of purity, one’s consciousness which is the purest light of wisdom shines through with clarity.
To objectively understand this process, you may visualise a vase made of glass. The glass is filled with light. When there is constant focus of energy on the glass in the form of heated contemplation, the glass shatters and completely breaks down. Yet the light within shines brightly even when the form is no more as it is independent of the glass.
Next visualise a lampshade made of silk cloth. Compare an idea to a wooden object that impacts the taut cloth which caves in forming a deviation in the path of the light. Now imagine a brightly lit room with an open space at the window ledge. An object passing through the window falls flat, making no dent or disturbance to the light that shines throughout the room.
The glass vase, the silk lamp and the brightly lit room with open windows are nothing but your own mind. The objects that are thrown are thoughts and ideas. Meditation is the process which purifies the memories which make the mind. In the beginning it is gross and impenetrable like wood, then it becomes glass, then yields like cloth and remains like empty space, merged with consciousness.
This state is Nirvitarka Samadhi, where consciousness shines through steadily through a pure mind. All the effort of yoga is to bring about this complete purification of smriti or memory. The memory indicated by smriti is of one’s true self as consciousness alone. This memory is always coloured by experiential impacts in consciousness. These impacts are caused not just by incidents happening around us sincWWe childhood, but mainly our reaction to those experiences.
At any point of time, the mind is coloured by guilt about the past, anxieties about the future and restlessness in the present moment. By constant efforts to purify the mind the three causes for restlessness—guilt, excitement and anxiety—are removed. When they are gone, the mind is its original self—steady and pure. There are no fidgety movements of the mind. In such a state, the pure consciousness is effulgent and speaks for itself.
(www.swahilya.blogspot.in)