Spanish water torture

Sometimes called the Toca, this was another favorite of the Spanish Inquisition.

The victim was tied to a rack that swiveled in the middle so that the head could be placed lower than the feet. The prisoner's head was strapped in place with an iron band, and his nose was sealed shut. A thick piece of cloth was stuffed into his mouth, and a steady stream of water was poured onto the cloth. The effect combined drowning and suffocation, all while the victim remained conscious and aware.

This is now better known as waterboarding, and it's used with far too much relish by the American military. 

In addition to the above writeup:

The victim was forced to swallow as much of the (water absorbent) cloth as possible before water was poured into the mouth.

The idea of pouring the water was to make the victim swallow and drag the cloth further down their throat. Eventually, the torturer would yank out the cloth causing unbearable pain.