Can someone check a quote from Unfinished Tales?

I'm doing a research paper on Tolkien, and I have the following quote:

Indeed, the Valar – gods of Middle-Earth – had ordered Gandalf’s kin never to “reveal themselves in forms of majesty” (Tolkien, “Unfinished Tales” 406?).

I got this quote from an online source I don't remember anymore, so I don't know which printing this is from... I'd really appreciate it if someone could find this passage in their Unfinished Tales and confirm the page number.

(And, if it's not too much trouble, the info on your copy, mainly the year of printing, edition, and publisher.)

Thank you!