Few of us get a good night’s sleep, but we all dream. What was different in Elizabethan times, though, was how humans thought about sleeping and dreaming. A new exhibit at the Folger Shakespeare Library shows just how differently Elizabethans examined dreams.

“To Sleep, Perchance to Dream,” using a phrase taken from William Shakespeare’s “Hamlet,” is the name of the Folger exhibit. Carole Levin, professor of history at University of Nebraska, and Garrett Sullivan, professor of English at Pennsylvania State University, began organizing the exhibit in 2007. The two worked together, with Levin working on dreams and Sullivan on sleep. The exhibit offers stories of potions and mythical creatures associated with sleep, but it also provides a wealth of interesting factual information pertaining to the times.

Even the act of sleeping was different in Elizabethan times. Since there was no electricity and candles were expensive, people went to bed when the sun set. But surprisingly, they often didn’t sleep through the night. Sullivan explained that Elizabethans would wake up in the middle of the night and stay up for an hour. Often they would socialize with neighbors during this time, and afterward, they would head back to bed, he said.

Another difference in Elizabethan times was the sense that people slept for different lengths of time depending on their “humor.” Elizabethans believed that there were four fluids in the human body, and if they were in balance, the person was healthy. But typically a person had an excess of one fluid.

These four humors also became personality types. If a person was sanguine, he had an excess of blood and was often light-hearted and good-humored. Choleric people had mostly yellow bile and were energetic, ambitious and born leaders. Those who were melancholic had an excess of black bile and were creative and sensitive to the tragedy in the world. Phlegmatic people had an increase in phlegm and were calm, unemotional and dry-witted. According to this theory, the sanguine and choleric people were expected to sleep for seven hours, while the melancholic and phlegmatic required nine hours of sleep because of their cold character.

Dream interpretations were sometimes based on this theory of humor. Richard Saunders wrote in the 1600s that a bad dream for a person of sanguine humor may actually be a good dream for a melancholic person. At the exhibit and on the Folger Web site, visitors can interpret their own dreams using a “dream machine.”

“We thought there were so many interpretations that it would be interesting and interactive,” Levin said.

While some dreams seemed to be particular to Elizabethan times, other themes — such as falling and flying — seem to have lasted through the centuries, Levin said.

While today people are comforted and excited by good dreams, in Elizabethan times people feared that dreams pertaining to their desires could be the devil tempting them. As a result, people sought to find ways to have pure and pleasant dreams. Wilhelm Adolf Scribonius wrote that the most pleasant dreams come as morning approaches, when the spirits are the most pure, a common theme throughout the exhibit.

There were also recipes to achieve good dreams. “If you want exciting dreams, just get an ape’s heart and put it under your pillow,” Levin said, adding, with a smile, that it was easier said than done. The same goes for ways to avoid nightmares. Edward Topsell wrote that to avoid nightmares, a person should eat the wine-soaked tongue or gall of a dragon. Thomas Nicols said that to avoid terrible dreams and evil thoughts, one should wear a ruby or, better yet, grind it up and drink it.

Shakespeare often wrote on the topic of sleep and dreams. One of the displayed manuscripts offers a recipe for “a dormant drink,” which would make a person sleep for two days.

“We wanted each case to be interesting,” Levin said. He and Sullivan worked through many ideas to tie the exhibit together until they came upon one that started with getting ready for bed and progressed through the night, ending the exhibit with waking up. This idea made it, as Levin said, “a journey through the exhibit.”

If visitors aren’t intrigued enough by the dreams, they may want to see another piece of history. The museum has the only copy of a manuscript by Richard Haydock, known as the “sleeping preacher,” who faked the act of preaching in his sleep.

Visitors may also want to be aware that, after seeing the exhibit, they will be hesitant to nap. William Vaughan warns, “sleeping at noon is very dangerous.” Hamlet’s father can vouch for that.

The exhibit will run through May 30 in the Folger Great Hall.