\documentclass{ppex}
\nonstopmode
\usepackage [curve,knot,dvips]{xy}
\pagestyle{empty}
\setlength\textwidth{231.0pt}
\begin{document}
\ResetPreambleCommands
\ReadyForTheFray
\usepackage [curve,knot,dvips]{xy}
\[\begin{xy} /r2cm/:(0,.5)::
 ,{\hcap-\huncross\hcap}
 ,+(1,0),{\vcap\vuncross\vcap-}
\end{xy}\]
\end{document}
