In 1851, the Reverend C. Chauncey Burr wrote in the "New-York Tribune" that by cracking toe joints the sounds were so loud, they could be heard in a large hall. In the same year three investigators Austin Flint, Charles E. Lee and C.B. Coventry from the University at Buffalo examined the raps produced by the sisters and concluded they were produced by cracking their bone joints such as toes, knees, ankles or hips. From a control, they discovered the raps did not occur if the sisters were placed on a couch with cushions under their feet.