Ok… think I’m on the right track. Spacing is a little off, but working on it.
Full style:
#toggle-nav::before {
background: #252525 none repeat scroll 0% 0%;
color: #FFF;
content: "TOC";
display: block;
padding: 7.425px;
position: fixed;
top: 50%;
transition: all 0.5s ease-in-out 0s;
left: 0px;
-webkit-transform: rotate(-90deg);
-moz-transform: rotate(-90deg);
-ms-transform: rotate(-90deg);
-o-transform: rotate(-90deg);
transform: rotate(-90deg);
/* also accepts left, right, top, bottom coordinates; not required, but a good idea for styling */
-webkit-transform-origin: 50% 50%;
-moz-transform-origin: 50% 50%;
-ms-transform-origin: 50% 50%;
-o-transform-origin: 50% 50%;
transform-origin: 50% 50%;
/* Should be unset in IE9+ I think. */
filter: progid:DXImageTransform.Microsoft.BasicImage(rotation=3);
}