Does anyone know how much weight an original womb chair holds?  

No need to fret.
Your guest can handle this one on his own. I guarantee that he'll take one look at the Womb's skinny little splayed-out legs and deep hard-to-struggle-out-of seat... And then he'll choose to sit on something else.

gah my eyes! First thing I th...
gah my eyes! First thing I thought
of when I saw that was Freuds paintings
of Leigh Bowery, which I like a lot,
but that I don't.

Leahy Bowery the surreal...
Leahy Bowery the surreal fashion designer?

Was just about to eat my...
Was just about to eat my lunch!

hahaha!
I know I've seen that photo before. It was an ad for some dealer, either in Atomic Ranch or Modernism.

Yes, David Skelley's shop.
Boomerang For Modern, in San Diego.

Self Portrait?
It that Mr. Skelley himself? Brave man.

Not a self-portrait.
David looks more like this:

That would have made
a better advertisement.

Appreciate the artistic humor, but I need a serious answer
I asked if anyone knows the maximum weight that an original womb chair holds. Unfortunately I don't have any other adequate seating for this guest because of size. Does anyone really know the weight that an original Knolls womb chair can hold? Maybe this is the wrong site to ask this question? If so, does someone know where I can go for an answer.

Weight limits for furniture i...
Weight limits for furniture isn't well documented if at all, unless they're industrial grade machine shop stuff. Since Knoll is still in business and continues to produce these chairs...inquire with them and report to us.

Lorraine
Ok, a serious answer:
1) Together, the wife and I weigh about 290 pounds. We just spent a couple minutes making out in our chair, and it didn't collapse.
2) In my experience, 300-pound people don't usually have THAT much trouble finding a chair to sit on; the seat of the Cone chair in the photo I posted earlier is only 16" in diameter, after all. Are you SURE that your guest can't fit on any of your chairs but the Womb? What sort of chairs do you have?
3) What I said earlier about the Womb's "deep, hard-to-struggle-out-of" seat is true; even if the chair can support him or her, your guest may find it very difficult to get in and out of.
4) There's lots of sturdy furniture available on Craigslist for not much money. If you're worried about your Womb chair, you could find a big lounge chair or recliner in the next few minutes and have it in your living room by this evening.
Good luck...