$\Newextarrow{\xhookrightarrow}{10,10}{0x21AA}$
8.57
\begin{equation} \begin{gathered}\label{diagram:Hom-witness-later} \xymatrix@R =50pt@C=50pt{ \{ X\} \times _{ \operatorname{\mathcal{C}}^{\operatorname{op}} } \operatorname{Tw}(\operatorname{\mathcal{C}}) \ar [r]^-{T_ X} \ar [d] & \{ \Delta ^0 \} \operatorname{\vec{\times }}_{\operatorname{\mathcal{S}}} \operatorname{\mathcal{S}}\ar [d] \\ \operatorname{\mathcal{C}}\ar [r]^-{ \mathscr {H}(X, -) } & \operatorname{\mathcal{S}}} \end{gathered} \end{equation}