Cannot add in text block

Hi guys.

I need to add a piece of code (see below) inside a text block just the way I do on a normal post. It seems that with the visual editor it converts this text to unstable code instead of leaving it as is.

<div id="wistia_mjf34zby6x" class="wistia_embed" style="width:728px;height:410px;"></div>
<script charset="ISO-8859-1" src="//fast.wistia.com/assets/external/E-v1.js"></script>
<script>
wistiaEmbed = Wistia.embed("mjf34zby6x", {
    trackEmail: theEmail
  });
</script>