Yes that title is correct. No one was more surprised at that 19th Century tidbit than I was. I first saw a posting on a manufacturer's list and it cited five companies making waterbeds. I'm thinking to myself that there has to be some sort of medical thing and sure enough they were advertised and used in hospitals and with doctors.
Below is a picture of an ad in The Lancet London ©1857 (can you believe that date? 1857? Amazing. imho)
Now I didn't find a listing for waterbeds being sold for homes but I found it interesting that waterbeds went as far back as the 19th century, perhaps longer, I don't know and haven't researched it. (actually they went back to the time of Alexander according to "The Family Cyclopaedia" ©1859 you can read the excerpt with this link
Below is an excerpt from "Practical Hints of the Management of the Sick-Room" ©1857
In all cases where a patient has to lie long in bed, or in acute cases attended with much debility, bed sores are very apt to form. These sores form on those parts of the body where the bones are least protected by flesh. They are not only very distressing to a patient, but very weakening, and frequently tend not a little to accelerate a fatal issue. To prevent them, perfect cleanliness is absolutely essential; but, in addition, some means must be used to take off the pressure from the more prominent parts of the body. For this purpose, various contrivances, in the shape of water-beds, and water and air cushions, are used. Hooper's water-beds are exceedingly useful, and very agreeable to the patient. The whole body floats, as it were, oh the water, and is buoyed up in such a manner as to equalize the pressure over the whole surface of the body. The bed should not be quite filled, and the water when first put in should be warm, otherwise the patient feels cold and chilled for a long time. Two or three blankets should, in cold weather, be laid under the patient, as the water is sure to get cold, and would make him chilly.
After having tried air-beds, water-beds, and spring-beds, I think the water-beds, on the whole, the most comfortable and the most useful. The spring-beds are not suitable in cases where movement disturbs the patient, as they are too elastic; and the air-beds are so exceedingly apt to get out of order, that they often fail just when they are most wanted. As an example of the efficacy of water-beds in preventing bed-sores, I may mention the following case:—A man came under my care, about a year ago, with acute gangrene or mortification of the legs; for this it was necessary to amputate both legs just below the knee; this I accordingly did on the same day. He was, of course, unable to lie in any other position than on the back; and to this position he was confined for five or six weeks until the stumps healed. During the whole period, although he was very weak from previous privation and the amputations, no bed-sores formed, nor was any inconvenience experienced from the decumbency. He attributed, and I think justly, no small share of his recovery to the water-bed.