hypnagogic

That induces sleep; soporific, somniferous.

That accompanies falling asleep; especially, pertaining to the semi-conscious period immediately preceding sleep.

But if we are in the right mood, a second of such lethargy is enough to make a hypnagogic [translating hypnagogische] hallucination appear, after which perhaps we reawaken, until the oft-repeated performance is brought to an end by sleep.

Very quickly it would come to seem to Lionel Hoffmann that the remainder of his life, all that was not Siri, was of little more substance than those hypnagogic images that flash against our eyelids when, in a state of exhaustion, we begin to sink into sleep.