The PicTeX manual
PicTeX is a set of macros by Michael Wichura for drawing diagrams and pictures. The macros are freely available; however, the PicTeX manual itself is not free. Unfortunately, TUG is no longer able to supply copies of the manual (as it once did), and it is now available only through [Personal TeX Inc](https://pctex.com/), the vendors of PCTeX. The manual is not available electronically.
However, there is a summary of PicTeX commands available on CTAN, which is a great aide-memoire for those who basically know the package to start with.
Source: The PicTeX manual