title: Set max on mongo capped collection
body: <p>I have an existing collection that I need to convert into a <a href="http://www.mongodb.org/display/DOCS/Capped+Collections" rel="noreferrer">Capped Collection</a> using the method listed:</p>
  
  <pre><code>&gt; db.runCommand({"convertToCapped": "mycoll", size: 100000});
  </code></pre>
  
  <p>However, the max field is not accepted as a parameter</p>
  
  <pre><code>&gt; db.mycol1.convertToCapped
  function (bytes) {
      if (!bytes) {
          throw "have to specify # of bytes";
      }
      return this._dbCommand({convertToCapped: this._shortName, size: bytes});
  }
  </code></pre>
  
  <p>Any idea how to set this?</p>