Problem with jQuery in post body?

When you are using Google CDN hosted version of jQuery then you don’t need to use jQuery wrapper. It’s for jQuery packed with WordPress core because jQuery with WordPress runs in noConflict mode.

So your jQuery code will be.

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<script type="text/javascript">
  $(document).ready(function() {
    console.log("Test");
    $(".myBox").click(function(){
        var myBoxOn = $(this).attr("data-class");
        $(".myBoxContent").hide("slow");
        $("#" + myBoxOn).show("slow");
    });
  });
</script>