959. O men who, caught by the dangerous snares of the world and struck by the sharp arrows of cruel miseries, are suffering greatly and are wandering in search of the attainment of supreme bliss, the sleep in which there is no loss of consciousness [i.e. wakeful sleep or jagrat-sushupti] alone is the imperishable happiness.

~Sri Ramana Maharshi, Guru Vachaka Kovai

Commentary by Sri Sadhu Om:

”The sleep in which there is no loss of consciousness’ [arivu-azhiya tukkam] means only the state of Self-knowledge.

‘Here consciousness [arivu] means prajna or the knowledge of one’s own existence, and not the knowledge of other things.

‘That which knows other things is not true knowledge [see Ulladu Narpadu verse 12]. The state we call sleep is the state in which we know no other things, not even the body.

‘The state we call waking is the state in which, along with the knowledge of one’s own existence [‘I am’], there is also knowledge of other things.

‘The state in which we remain conscious merely of our own existence, like in waking, but in which the mind [the knower of other things] does not rise, like in sleep, is called the state of conscious sleep or wakeful sleep.

‘Since no other thing is known in this state, it is a sleep; and since one’s own existence is shining clearly there, it is a state of consciousness or waking.’

960. Those who are sleeping, having given up the habit of [going out through] the deceitful senses and having become established in the heart-lotus, are those who are awake in the abode of real knowledge [mey-jnana]. Others are those who are asleep, being immersed in the dense darkness of this unreal world [poy-jnala].

~Sri Ramana Maharshi, Guru Vachaka Kovai