I have a paper that I've written in response to an essay on water torture that appeared in the Columbia Journal of Transnational Law--but I haven't pursued publication of that work as yet.
However ('bout time I got to the point!), I did find a historical reference to the "water cure" that at least has some bearing on suffocation/drowning as a form of torture. Henry Smith Williams wrote in 1907 about the tortures used by the Spanish inquisitors in a booklet called "On Spanish Inquisition and Torture."
Williams wrote first about the "tormento di toca" taking place on the "wooden horse." Williams' explanation of the "wooden horse" was less than clear so I'll reproduce a slightly better one from Blackwood's Magazine (1926):
... is analogous to the French Chevalet and the English Wooden Horse. The instrument by which it is inflicted consists of wood, made hollow like a trough, so as to contain a man lying on his back at full length, and is without any other bottom than a round bar laid across, which, moreover, is so situated that the back of the person to be tortured must rest upon the bar, instead of the bottom of the trough, while, by its peculiar construction, his feet are raised much higher than his head. When the patient is placed in this apparatus, his arms, thighs, and ankles, are made fast to the sides by means of small cords, which, being tightened by means of garrots, or rackpins, (called by some the Spanish windlass,) in the same manner, precisely as carriers tighten the ropes that fasten down the loads on their carts, cut into the very bones, so as to be no longer discernible. Que sera-ce lorsqu'un bras nerveux viendra mouvoir et tourner le fatal billot? The sufferer being in this situation, the most unfavourable that can be imagined for performing the function of respiration, there is inserted deep into his throat a piece of fine moistened linen, upon which an attenuated stream, or thread of water, descends from an earthen vessel, through an aperture so small that little more than an English pint is instilled in the course of an hour.The risk of using this reference consists of the relatively strong chance that Williams' booklet was used as one of the primary sources. Williams' account, however, does less to suggest that the thin cloth is inserted into the throat ("the torturer throws over his mouth and nostrils a thin cloth. so that he is scarce able to breathe through them")--but somehow the cloth ends up there anyway ("When this cloth is drawn out of his throat, as it often is, that he may answer to the questions, it is all wet with water and blood, and is like pulling his bowels through his mouth").
(Blackwood's Magazine, vol. XX, (July 1826), pp. 70-89.)
Now Williams on the "water cure":
... when night came on his fetters were taken off, then he was stripped naked, put upon his knees, and his head lifted up by force; after which, opening his mouth with iron instruments, they filled his belly with water till it came out of his jaws. Then they tied a rope hard about his neck, and in this condition rolled him seven times the whole length of the room, till he almost quite strangled. After this they tied a small cord about both his great toes, and hung him up thereby with his head down, letting him remain in this condition till all the water discharged itself out of his mouth, so that he was laid on the ground as just dead, and had his irons put on him again.The "tormento di toca" bears the greater resemblance to modern waterboarding, though I have no indication that the latter allows cloth or anything else besides water to enter the throat. In accordance with that, the feeling of the victim having his bowels pulled out through his mouth would be absent.
The description of the "water cure" as used by the Catholic inquisitors bears considerable resemblance to the "water cure" used in Philippines (and adopted by the U.S. to aid counterinsurgency there in the early 20th century) and later by the Japanese during World War II. Both end up with the victim swallowing large amounts of water, with the water being later forced out by another torture technique (the Japanese often simply applied pressure to the stomach instead of hanging the victim upside-down).