Sleep. That most mysterious of times. The unconscious hours.Everyone needs it. Whether it's the recommended eight hours, forty winks, cat naps, power naps or other shades of blissful slumber. Sleep offers a respite from the rigors and challenges of the day. A chance for the brain to process what has happened and bring rest and recuperation before the cycle of daytime activity begins again.Also, perchance to dream or, if we are unlucky, the visitation of nightmares.But for some people sleep does not come easy. These can be wakeful hours of frustration or tedium where closing the eyes does not bring the closing of the mind and the slumber so keenly wanted.Part of the problem, in this increasingly frenetic 24/7 world is that we seem reluctant or unable to switch off enough to recuperate; we might miss something. But slumbered hours bring gains in health that far outweigh transitory loss.Our poets from Kipling and Swinburne through Hafiz, James Joyce, Edgar Allan Poe and a pillowful of others explore the wish to rest, to close the eyes and reside in the land of nod.