An archival markup language for math and the classics; compiles to LaTex and HTML. Designed for the bourbaki project and the Litterae of the great books. For more information, see littex.org.
Here's an exampe of some LitTex from Halmos' Naive Set Theory:
¶ ⦊
‖ The principal concept of set theory, the one that in
completely axiomatic studies is the principle primitive
(undefined) concept, is that of ‹belonging›. ⦉
‖ If $x$ belongs to $A$ ($x$ is an element of $A$, $x$
is contained in $A$), we shall write
◇ ⦊
‖ x ∈ A. ⦉
⦉⦉
‖ This version of the Greek letter epsilon is so often
used to denote belonging that its use to denote
anything else is almost prohibited. ⦉
‖ Most authors relegate $ϵ$ to its set-theoretic use
forever and use $ε$ when they need the fifth letter of
the Greek alphabet. ⦉
⦉