$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
10.21
\begin{equation} \begin{gathered}\label{equation:poset-not-universal} \xymatrix@R =50pt@C=50pt{ \{ a, d \} \ar [r] \ar [d]^{f_0} & Q \ar [d]^{f} \\ \{ 0 < 2 \} \ar [r] & [2]. } \end{gathered} \end{equation}