Prisons are places of suffering. But in theory, they aim for something beyond punishment: reform.

In the United States, the goal of prisoner rehabilitation can be traced back, in part, to the 1876 opening of the Elmira Reformatory in upstate New York. Purported to be an institution of “benevolent reform,” the reformatory aimed to transform prisoners, not just deprive them—though founder Zebulon Brockway, known as the “Father of American Corrections,” was notoriously harsh.

Other states soon adopted the reformatory model, and the notion that prisons are places to “correct” people has become a staple of the judicial system.

But the idea that imprisonment and suffering were supposedly good for the prisoner didn’t emerge in the 19th century. The earliest evidence goes back some 4,000 years: to a hymn in Mesopotamia, in modern-day Iraq, praising a prison goddess named Nungal.

Almost a decade ago, as a graduate student researching slavery in early Mesopotamia, I came across numerous texts dealing with imprisonment. Some were administrative documents dealing with everyday accounting information. Others were legal texts, literature or personal letters. I became fascinated with imprisonment in these cultures: Most of them detained suspects only briefly, but in literary and ritual texts, imprisonment was seen as a transformative, purifying experience.