<!doctype html>
<html>
  <head>
    <title>phantom</title>
    <meta charset="utf-8"/>
  </head>
  <body style="background: white;">

    <!-- The <mphantom> element should be invisible but should have the size
         of its content. -->
    <math>
      <mfrac>
        <mtext>mphantom</mtext>
        <mrow>
          <mo>[</mo>
          <mphantom>
            <mo>(</mo>
            <mn>2</mn>
            <mo>+</mo>
            <msqrt>
              <mfrac>
                <mi>x</mi>
                <mi>y</mi>
              </mfrac>
            </msqrt>
          </mphantom>
          <mo>]</mo>
        </mrow>
      </mfrac>
    </math>

</body>
</html>