Example
Heading 1
Heading 2
Heading 3
Heading 4
Heading 5
Heading 6
Markup
<h1>Heading 1</h1>
<h2>Heading 2</h2>
<h3>Heading 3</h3>
<h4>Heading 4</h4>
<h5>Heading 5</h5>
<h6>Heading 6</h6>
Source:
text/fonts.less
, line 136