Setting the cursor in an iframe from another iframe

[Laura]

How do I set the cursor in one iframe from another iframe?

I'm trying to change the cursor to an hourglass in all the frames of a
certain window. Because of horrendous design early on, this window
contains two iframes, one of which contains another iframe. The
action that triggers the need for the hourglass is initiated from the
innermost iframe.

Unfortunately, no matter what I try I can't seem to get the cursor to
change in the iframes. It changes in the top window, but none of the
others:

// This works:
top.document.body.style.cursor = "wait";

// None of the following work
// As you can see, I tried bottom-up and top-down brute force
self.document.body.style.cursor = "wait";
parent.document.body.style.cursor = "wait";
parent.parent.document.body.style.cursor = "wait";
top.frames[0].document.body.style.cursor = "wait";
top.frames[0].frames[0].document.body.style.cursor = "wait";
top.frames[0].frames[1].document.body.style.cursor = "wait";

Is there some restriction on cursor styles in iframes?