%%
%% The LaTeX Companion, 3ed
%%
%% Example 9-6-1 on page I-707 in "Setting up the main document font families".
%%
%% Copyright (C) 2022 Frank Mittelbach
%%
%% It may be distributed and/or modified under the conditions
%% of the LaTeX Project Public License, either version 1.3c
%% of this license or (at your option) any later version.
%%
%% See https://www.latex-project.org/lppl.txt for details.
%%

\documentclass{tlc3exa}
\pagestyle{empty}
\setcounter{page}{6}
\setlength\textwidth{167.0pt}

%!TEX program = lualatex

%StartShownPreambleCommands
\usepackage{fontspec}  \setmainfont{Optima}
%StopShownPreambleCommands

\begin{document}
This \textbf{text} is typeset in the \emph{system font}
Optima. \textsf{Sans Serif} and \texttt{Typewriter}
still default to Latin Modern Sans and Typewriter.
\end{document}