Old LaTeX font references such as `\tenrm`
LaTeX 2.09 defined a large set of commands for access to the fonts
that it had built in to itself. For example,
to the size it's being typeset at.
These commands were never documented, but certain packages
nevertheless used them to achieve effects they needed.
Since the commands weren't public, they weren't included in LaTeX2e; to use the unconverted LaTeX 2.09 packages under LaTeX2e, you need also to include the rawfonts package (which is part of the LaTeX2e distribution).