%%
%% The LaTeX Companion, 3ed
%%
%% Example 9-6-12 on page I-718 in "Vertical positioning features".
%%
%% 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{81.0pt}

  %!TEX program = lualatex

  \setlength\parindent{0pt}

%StartShownPreambleCommands
\usepackage{fontspec}
\setmainfont{Alegreya}
\newcommand\textsu[1]{{\addfontfeature{VerticalPosition=Superior}#1}}
\newcommand\textin[1]{{\addfontfeature{VerticalPosition=Inferior}#1}}
%StopShownPreambleCommands

\begin{document}
Catch\textsubscript{22} in Room\textsuperscript{13}% inferior quality

Catch\textin{22}        in Room\textsu{13}         % much better!
\end{document}