What is wrong with that code in picture environment? It does not show of the lines, just the labels

Question

\setlength{\unitlength}{0.25mm}
\begin{picture}(400,140)
\put(50,20){\begin{picture}(100,100)
 \Thicklines
 \path(0,0)(100,0) \path(90,-5)(100,0)(90,5)
 \path(0,0)(0,100) \path(-5,90)(0,100)(5,90)
 \path(0,0)(92,40) \path(82,40)(92,40)(86,32)
 \path(0,0)(-40,92) \path(-40,82)(-40,92)(-32,86)
 \thinlines
 \dottedline(0,0)(-40,0)(-40,92)(0,92) \dottedline(0,40)(92,40)(92,0)
 \put(110,-5){\scriptsize $\ep_1$}
 \put(-5,110){\scriptsize $\ep_2$}
 \put(97,42){\scriptsize $\ep_1'$}
 \put(-50,100){\scriptsize $\ep_2'$}
 \put(82,-20){\scriptsize $\cos\theta$}
 \put(5,43){\scriptsize $\sin\theta$}
\end{picture}}

\put(250,70){$\ep_1'=\cos\theta \ep_1+\sin\theta \ep_2$}
\put(250,40){$\ep_2'=-\sin\theta \ep_1+\cos\theta \ep_2$}
\end{picture}