mspace-01.mml

<?xml version='1.0' ?>
<math display="block" xmlns="http://www.w3.org/1998/Math/MathML">
  <mrow>
    <mtext mathvariant="normal">First line</mtext>
    <mspace width="0.0em" />
    <mtext mathvariant="normal">Second line</mtext>
  </mrow>
</math>