From the Clarksville Star, Clarksville, Iowa; April 25, 1878:
A good deal of whispering took place on the sidewalk Thursday afternoon. I twas through a telephone on exhibition by Mrs. Mulinex. The instrument was stretched from the postoffice to the STAR office. You stuck your mouth into a starch-box at one end, and someone at the other end, stuck their ear into another starch-box, the "connecting link" being a black thread. The sound was quite distinct.
I want to type up a transcription of the news article telling about selling George Washington's library, but it's rather long.