What is "powdering tub"

Powdering \Pow"der*ing\, a. & n. from Powder, v. t. Powdering tub.

1. A tub or vessel in which meat is corned or salted.

2. A heated tub in which an infected lecher was placed for cure. [Obs.]
   --Shak.

n. 1 (context archaic English) a tub in which the meat was powdered or salted; a salting tub, pickling tub or powdering trough. 2 (context obsolete English) A heated tub for the treatment of venereal disease by sweating. 3 (context obsolete slang English) the pocky Hospital at Kingsland near London.