Vijnana Bhairava Tantra · Dharana 52 · Verse 75
Threshold of sleep
Lie down, or sit, as sleep approaches. There is a brief threshold where the outer world has already faded and sleep has not yet taken you. Stay in that interval. Do not drop into sleep, and do not haul the day back. This sits close to dream practice, but it is not dream practice. The in-between itself is the meditation.
Older line
When sleep has not yet come and the outer world has already faded, that state can be reached by the mind. There the Supreme Goddess shines.