Here is a fascinating if grim illustration of a punishment used in Auburn State Prison, New York, in 1858. The description reads:
"The convict, More, was a negro. He is certified to have been a man of naturally pleasant temper, but violent when crossed ... he was dragged by main force, and after many violent struggles, to the shower-bath; all the water that was in the tank -- amounting to from three to five barrels, the quantity is uncertain -- was showered upon him in spite of his piteous cries; a few minutes after his release from the bath he fell prostrate, was carried to his cell, and died in five minutes."
This page adds:
The use of the shower-bath as a means of coercing criminals into submission to the orders of prison authorities began to be general about the year 1845.
This is not torture, then, because it isn't used to extract information, just to crush a human spirit and body. But it is awful nonetheless.