Skimming the help.gnu.emacs newsgroup can turn up all sorts of amazing
tidbits. For example, I occasionally write papers using the LaTeX
markup language for scientific documents. This allows me to produce
professional-quality typeset papers, particularly when equations are
involved. (I used that *so* many times in university!)

I just found out that you can click on the typeset document (the DVI)
and jump to the source code. Here’s what David wrote on help.gnu.emacs:

That’s easy. This feature is called forward and inverse search. It’s
explained in the AucTeX manual. If you use auctex just hit C-c C-t C-s
(I don’t know if this also works within the build-in tex mode). This
enables the TeX-source-specials. With the source-specials on, Emacs
will start xdvi with further options. xdvi will start displaying the
page where the point is set in Emacs (forward search). When you click
any line in xdvi simultaneously pressing Ctrl you return to Emacs with
the point on the corresponding paragraph. This works also with other
dvi viewers, but you have to configure them to use emacs server for
inverse search.

Wow.

Random Emacs symbol: default-fringes-outside-margins – Variable: Default value of `fringes-outside-margins’ for buffers that don’t override it.