Like Einstein’s intelligence, there are some old html scripts that continue to work in this ever changing cyber world in which we live. It may require tweaking because of your CSS sheet, but for now, it’s still doable.
Below is the script, followed by how it will display. Enjoy!
<span style="margin-top: 20px; font-size: 60px; background: firebrick; float: left; line-height: 40px; margin-right: 6px; border: black 1px solid; padding: 20px">E=mc²</span>