There's a great review in the New York Times of an exhibition “To Sleep, Perchance to Dream,” which has opened at the Folger Shakespeare Library in Washington.
It reveals the complexities of the way that sleep was seen in the 17th century, not as something functional and rather trivial, but as an uncertain and thought-provoking state. "Sleep should not be thought of casually: it is mysterious, powerful, central, inextricably linked to the world."
This exhibition shows how seriously the men and women of the 17th century took their sleep - recognising that it needed to be attended to as much as their waking hours.
There is a marvellous quote from the 1630s, saying that the wise man "learnes to know himselfe as well by the night's blacke mantle, as the searching beames of day. In sleepe, wee have the naked and naturall thoughts of our soules".
You could sit back and think about that for a long time. While we attach so much status to what we achieve in our work and in our public lives, to what we show other people, it's under night's black mantle that we might see more of our own souls.
There are also some intriguing sleep remedies. There was the old stand-by of poppy, but also lettuce and dormouse blood. Both lettuce and dormice have been associated with sleep forever, they are remarkably persistent associations.
The exhibition runs until the end of May - and there is some information online at http://www.folger.edu.