Helmholtz's 1858 paper is a PDF on Google under the name I gave.
I like your sarcasm, but I hope nobody misinterprets it as trolling. That would be incongruous in a mentor.
Thinking more about that rule, in this case it seems to be having the undesirable effect of stifling a discussion because the answer is not readily available on Google. I'd have thought that was precisely the factor that makes it worthy of discussion.
There probably are papers from the 19th century but they're lost in the mists of time now, or perhaps the letters section of New Scientist already dissected this topic ad nauseam in the 1970s, but nobody in this thread seems to know where that stuff is, so we'll just have to figure it out from scratch.
If I mentioned a theory of my own, I don't claim exclusivity in that, I think everybody can have their own take on this everyday experience. Even my three year old son has a theory: he thinks it's electric. The rest of us might not be making much more sense, but until some eminent scientist decides that plugholes are better for his career than dark matter, we'll just have to muddle along.
A phenomenon that everybody can experience without digging up half of Switzerland, can think about intuitively without an arsenal of mathematical machinery, and can experiment on just by cutting a hole in a bucket, seems to me like just the kind of topic that amateur science is here for.