I do not have any research or a definite answer for you, but I think that you will not be able to find them. The main problem is that the "reasonable" is subjective. In addition, a document that has a βreasonableβ speed for you in one browser can be much slower in another (thnk about speed differences between only major browsers like IE, firefox, chrome and safari).
You also need to think about how fast the network connection is for users trying to download your html document. I am sure that most people have fast enough Internet now, because several MB files are not big, but not everyone does, and even for those who have fast Internet, if your html starts to rise to a couple of hundred MB or GB +?
There are many variables that will affect how slowly your HTML document loads / renders, and I think that ultimately the only way to justify is that your users are willing to put up with it. Just my 2cents.
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