[jQuery] How do I trigger the click event on a button in another frame?

[Daemach]

This started out as just a quick hack until I can redo the mechanism
correctly, and now I just want to know how it works.

$(window) has no properties, so $(window.frames[1].document) has no
properties.  Oddly, window.frames[1].document in firebug pulls the
correct document.  I've been trying to make the following work to no
avail.  Is jQuery limited to the current document by design?

$
('input:[EMAIL PROTECTED]',window.frames["mainFrame"].document).click();