It's surprisingly hard to do. Since the allowed styling does not affect positioning in any way (you used to be able to change the font-weight, but not anymore)

It's surprisingly hard to do. Since the allowed styling does not affect positioning in any way (you used to be able to change the font-weight, but not anymore) and the browser removes all :visited styling for client side html-image libraries such as html2canvas you need to generate a massive amount of clicks from the user or have them targeted only to visited elements such as this page does.