  Rare meson decay experiments promise to measure branching ratios as small as
$10^{-13}$. This presents an opportunity to discover the $\mu^+\mu^-$ bound
state true muonium. We consider a set of possible channels, all with branching
ratios above $\sim10^{-11}$. For the electromagnetic decays
$\eta/\eta'\rightarrow(\mu^+\mu^-)\gamma$, theoretical and phenomenological
form factors $F_{\eta/\eta'\gamma\gamma^*}(Q^2)$ allow predictions of
$\mathcal{BR}(\eta'\rightarrow (\mu^+\mu^-) \gamma)\sim 4.8\times10^{-10}$ and
$\mathcal{BR}(\eta'\rightarrow (\mu^+\mu^-) \gamma)\sim 3.7\times10^{-11}$ at
the 5% level. Discussion of experimental prospects and potential backgrounds
are made.
