I just wanted a simple language for writing down algorithms, so I think I hacked up the first version in one afternoon. It must have been T2, because AFAIR I never implemented T1. Here is a page containing some of the past T3X compilers: http://t3x.org/t3x/ and here is an incomplete and inaccurate history of T3X: http://t3x.org/t3x/family.html