Loading partial after page loads

For performance reasons, I need to render a partial asyncronously
(after the page loads). I've already isolated the code into a
partial, but I haven't figured out how to render it after the page
loads. Do I have to fire off the onload event in raw javascript? Any
ideas how to do this? It seems like a common problem, but I haven't
seen any solutions online for this.

Thanks,
Scott