Have mercy, Jesu! Soft! I did but dream. O coward conscience, how dost thou afflict me! Thus spoke Shakespeare’s Richard III on stirring from a dream that predicted his downfall in the battle of Bosworth Field. Such prophecies are central in “To Sleep, Perchance to Dream,” the Folger’s new installation on the Elizabethan culture of sleep, in which the interpretation of dreams wasn’t Freudian navel-gazing but a sure-fire gauge of one’s sexual, professional, and political prospects—even one’s prospects for redemption. Besides the “Dream Machine”—a computer console that spits out period-appropriate analyses based on a visitor’s touch-screen inputs—the Folger presents manuals on widely accepted folk remedies of the day: For insomnia, take poppies, lettuce, and a vinous distillation of dragon’s tongue, plus the storied mandrake root, whose effects John Donne described so pleasantly as “betwixt sleep and poison.” Sure, most of these treatments fall into the “don’t try this at home” category of homeopathy, but then, you don’t watch Rome for the history lessons, either.

THE EXHIBITION IS ON VIEW MONDAY TO FRIDAY, 10 A.M.–5 P.M., TO MAY 30, AT THE FOLGER SHAKESPEARE LIBRARY, 201 EAST CAPITOL ST. SE. FREE. (202) 544-4623