This is what Spyglass shows for the site domsalumni-iitm dot org (a PR7 site):
The site has 10 backlinks going to it, but 6 of those are either missing or nofollow.
That leaves 4 backlinks that carry any juice. 3 of those are PR0, so you know that the only link that is carrying any real weight is the PR8. It comes from the homepage of a technical school in India.
I wanted to point this out just to show that all you need is ONE backlink to bring you a PR-whatever.