Is there a way to draw a simple circle or square in plain TeX/LaTeX, without relying on graphics packages?

As long as you only want the circles in a limited size range

\documentclass{article}

\begin{document}


zzz
\begin{picture}(8,8)
  \put(5,3){\circle{5}}
\end{picture}
zzz
\begin{picture}(8,8)
    \put(5,3){\circle*{5}}
\end{picture}
zzz
\begin{picture}(8,8)
    \put(1,1){\framebox(5,5){}}
\end{picture}
zzz

\end{document}

 \documentclass{article}
\usepackage[T1]{fontenc}
\begin{document}
\textbullet \rule{1ex}{1ex} \Huge\textbullet \rule{1ex}{1ex} 
\end{document}