Ducking Stool
2 of the 7 encyclopedias on this shelf carry an entry for Ducking Stool. Both are reproduced below, so you can see where they agree and where they differ.
Aiton's Encyclopedia (1910)
a contrivance for dipping common scolds under water. A chair was fastened securely to one end of a long sweep or pole mounted on a post by the shore of a pond or other body of water. The scold was tied into the chair amidst the plaudits of the rabble. An officer at the other end of the sweep whirled it around until the seat hung over the water, then worked his end up and down , churning the unfortunate culprit into and out of the water, amid a volley of oaths and vituperation, until the habit of scolding was overcome for the time at least. This relic of a coarse age was used generally in England at the time of the colonization of America, and it was introduced in the American colonies, both north and south. Its employment was not given over entirely until as late as 1806. See Pillory
Collier's New Encyclopedia (1921)
a chair in which scolding and vixenish wives were formerly securely fastened, to receive the punishment of being ducked in water. The woman was placed in the chair with her arms drawn backward; a bar was placed across her back and inside her elbows, while another bar held her upright; in this uncomfortable position she was securely tied with cords. The persons appointed to carry out the punishment, by raising their end of the beam, caused the unfortunate culprit to go overhead into the water. The practice of using the ducking stool began in the 15th century, but had almost died out by the close of the 18th.