 <math displaystyle="true">
      <!-- large operator -->
      <mo largeop="true" style="visibility: hidden">⥯</mo>
    </math>
    <math>
      <mrow>
        <!-- stretchy, small size -->
        <mspace height="2em"/>
        <mo style="visibility: hidden">⥯</mo>
      </mrow>
    </math>
    <math>
      <mrow>
        <!-- stretchy, large size -->
        <mspace height="4em"/>
        <mo style="visibility: hidden">⥯</mo>
      </mrow>
    </math>
    <div id="dynamic">
      <math>
        <!-