\documentclass[convert=true,convert={convertexe={convert},density=1200,outext=.png}]{standalone}

\input{figsDefs.tex}

\begin{document}
	
\begin{tikzpicture}%
	\fill[gray!40] (0,0) {[rounded corners=4pt] -- (0,1) -- (2,1) -- (2,.6) -- (2,3)
		-- (2.4,3) -- (2.4,.6) -- (2.4,1) -- (4,1)} -- (4,0) -- cycle;
	\draw (.5,.4) node {Hg};
	\draw (.8,2) node {air \`{a} $p_a$};
	\draw (2.2,3.3) -- +(1,.2) node[right] {$p\cong 0\,\text{Pa}$};
	\draw (0,1.4) -- (0,0) -- (4,0) -- (4,1.4);
	\draw (2,.6) -- (2,3.6) -- (2.4,3.6) -- (2.4,.6);
	\draw[<->,>=latex] (2.6,1) -- (2.6,3) node[right,pos=0.5] {$h$};
	\draw[dashed] (2.2,1) -- (4.5,1);
\end{tikzpicture}%

\end{document}