How to take a screenshot of a scrolling element within a web page in Firefox?

I need to take a screenshot of an entire webpage. The trick is that I need the screenshot to include the entire contents of a single element that does not fit in the screen.

It is a single column table that has a scrollbar due to it's height. It is not an IFRAME.

The column contains formatted text and a few small images.

For long web pages that scroll, it is trivial to perform this task. But how can it be accomplished when it contains an individual element within the page that scrolls?

I would like to accomplish this using Firefox on Windows.