[XeTeX] Unicode, infinity, TeXShop and XeTeX

[Stephen Moye]

I am using Hoefler Text in plain TeX in TeXShop. I need to use the 'infinity' sign (in Unicode Mathematical Oerators, position 2210E, at least according to the Mac Character Palette) and cannot for the life of me figure out how to get it. 

This is that last piece of a puzzle I've been working on, and any pointers would be gratefully recieved.

Thanks.

Stephen Moye