  On page 206 in his lost notebook, Ramanujan recorded the following enigmatic
identity for his theta function $\varphi(q)$: \begin{equation*}
\varphi(e^{-7\pi\sqrt{7}}) = 7^{-3/4}\varphi(e^{-\pi\sqrt{7}})\big\{1 +
(\quad)^{2/7} + (\quad)^{2/7} + (\quad)^{2/7}\big\}. \end{equation*} We give
the three missing terms. In addition, we calculate the class invariant
$G_{343}$ and further special values of $\varphi(e^{-n\pi}),$ for $n = 7, 21,
35,$ and $49$.
