Also saw Potter's "Mesmer" and I don't remember who said it where, but this doesn't have a very high reputation. I understand--as someone at imdb.com put it, Mesmer doesn't cure anyone, doesn't have any lasting successes, convinces no one of his powers. Potter gives Mesmer his full anti-glamour treatment, and the film (by Roger Spottiswoode, who I think is pretty good, but not at this sort of thing) is stubbornly dark and grim.
Still, I do think something does shine through--the argument made that imagination and the mind have as much effect on the body as mere drugs might be something Potter would champion (and probably is the reason he was interested enough in the character to do this script), and the relationship between Alan Rickman's Mesmer and a blind girl is, when all is said and done, touching in its fragility. I wouldn't know how accurate this is about Mesmer's real life, but it's indubitably a work of Potter's.