I came across an interesting except from Abraham Lincoln on the meaning of "all men are created equal", from his debates with Douglas. I got this from a comment here. There seem to be a few typos, but I'm leaving it as the commenter had it.
Justice Taney, in his opinion in the Dred Scott case, admits that the language of the Declaration is broad enough to include the whole human family, but he and Judge Douglas argue that the authors of that instrument did not intend to include Negroes, by the fact that they did not at once, actually place them on an equality with the whites. Now this grave argument comes to just nothing at all, by the other fact, that they did not at once, or ever afterwards, actually place all white people on an equality with one or another. And this is the staple argument of both the Chief Justice and the Senator, for doing this obvious violence to the plain unmistakable language of the Declaration. I think the authors of that notable instrument intended to include all men, but they did not intend to declare all men equal in all respects. They did not mean to say all were equal in color, size, intellect, moral developments, or social capacity. They defined with tolerable distinctness, in what respects they did consider all men created equal -- equal in "certain inalienable rights, among which are life, liberty, and the pursuit of happiness." This they said, and this meant. They did not mean to assert the obvious untruth, that all were then actually enjoying that equality, nor yet, that they were about to confer it immediately upon them. In fact they had no power to confer such a boon. They meant simply to declare the right, so that the enforcement of it might follow as fast as circumstances should permit. They meant to set up a standard maxim for free society, which should be familiar to all, and revered by all; constantly looked to, constantly labored for, and even though never perfectly attained, constantly approximated, and thereby constantly spreading and deepening its influence, and augmenting the happiness and value of life to all people of all colors everywhere. The assertion that "all men are created equal" was of no practical use in effecting our separation from Great Britain; and it was placed in the Declaration, not for that, but for future use. Its authors meant it to be, thank God, it is now proving itself, a stumbling block to those who in after times might seek to turn a free people back into the hateful paths of despotism. They knew the proneness of prosperity to breed tyrants, and they meant when such should re-appear in this fair land and commence their vocation they should find left for them at least one hard nut to crack. I have now briefly expressed my view of the meaning and objects of that part of the Declaration of Independence which declares that "all men are created equal.
This quote is interesting in a number of ways. It serves to distinguish between original meaning and original application, which is why the commenter brought it out in a discussion of those. (For what seems to me to be the right take on those issues, see Larry Solum. The hat tip on all of this goes to Randy Barnett.)
The short of it is that originalists distinguish between original intent and original meaning as everyone would understand it (in terms of what philosophers call the sense or intension of a term) but fail to distinguish a third element, original application (what philosophers call reference or extension). Two people might understand the sense of the term 'cruelty' in the same way but apply the term to different sets of things, which means cruel and unusual punishments won't involve a clear set of punishments with absolutely determinate boundaries. There will be a penumbra, in other words (and those who make fun of the use of this term in living constitution contexts sound philosophically ignorant). That's what happens with vague terms. You can identify clear cases, but some cases will not be so clear, and borderline cases might or might not be cruel. I have no problem with this, nor should any originalist, as Solum points out. Vagueness of terms is simply part of human language, and a vague term like 'cruel' can be understood in its original sense while admitting that its extension is vague. Not every case we can ask about will have a determinate answer. That doesn't, however, mean that we're not going by the original understanding of what it is to be cruel. It's not as if we're inventing new meanings for the term as we discover new standards in society, as the living constitutionalists would have it. But that doesn't mean there aren't penumbras. That's just a matter of linguistic fact, since the only language we have to write a Constitution in is a vauge language.
So I don't think this distinction is a problem for an originalist view. What it's a problem for is those who can't distinguish between original understanding in terms of sense and original understanding in terms of reference. Lincoln's example is helpful. Jefferson used this expression "all men are created equal". There are two elements of how to take this. One is the issue of what "all men" means. Does it really mean all people, or does it simply mean adult males? Does it really mean all, or does it mean just all of a restricted class? Second is what it means to be created equal. Does it mean equal in every sense? Does it simply mean equal in a specific set of characteristics?
Taney and Douglas argued that the Declaration never meant to include blacks or other members of white families besides the head of household. Their argument relies on failing to distinguish between original meaning or the term itself (its sense anyway) and the application of the term (which things fall under the term). Their argument assumes that the things people applied it to wholly determines what the term itself meant at the time, and that just doesn't follow. So there's no reason to think the extension of 'all men' doesn't include women, children, and non-whites simply because it wasn't applied to those people. There's nothing in the context that limits its reference to those things, and the inclusive meaning of 'men' as humans was quite common in those days. Feminist arguments in the last 40 years or so (e.g. Catherine MacKinnon and Andrea Dworkin) have relied on the same linguistic fallacy.
At the same time, there is something in the context that restricts the meaning of 'equal'. The Declaration itself tells us what this means. As Lincoln observes, it would be stupid to assume that it meant that everyone is absolutely alike in every respect. People have different skin color. People have different sorts of abilities and capacities. I've heard this statement described as a noble lie, because it's clear that we're not all equal, yet it's important to act as if we are. Well, that ignores the different ways something can be equal. In this case, we have equal rights. In particular, we have the rights to life, liberty, and the pursuit of happiness. In this particular document, I think it's clear that Jefferson and those who endorsed his language meant that we have moral rights that they (wrongly, by and large) didn't think the British government was observing. There are two ways that even an original understanding of these rights wasn't applied properly. One was that some people who would originally have been included who in practice weren't being included even of having these basic rights. It wasn't applied properly. That doesn't mean it wouldn't have been understood by an ordinary reader or hearer at the time as including those people. Second, even Jefferson was misapplying them if he thought charging higher taxes on tea or housing soldiers in someone's home counts as a violation of the basic moral rights to life, liberty, and the pursuit of happiness. Surely some of the things the British were doing were wrong, and I wouldn't want them doing a number of things the colonists didn't want them doing, but it doesn't violate these basic moral rights.