getting the first line of text in an element jquery

I have an example element like this:

<div id="element">
  Blah blah blah.
  <div>Header</div>
  ...
</div>

it can also look like this:

<div id="element">
  <span>Blah blah blah.</span>
  <h4>Header</h4>
  ...
</div>

I want to get the first line (defining line loosely) (Blah blah blah.) of text inside the element. It might be wrapped inside a child element or just be naked textnode. How do I do that? Thanks.