[jQuery] text of first sibling of a parent...How do I get it

[con-man-jake]

Still a newbie.
I have this:

<table>
   <tr>

      <td>
         text I want to get
      </td>

      <td>
      </td>

      <td>
         <div id="knowndiv"></div>
      </td>

   <tr>
</table>

If I have the div with id of "knowndiv" as an object (call it "obj"),
How do I get the text inside the first <td>?