  We comment on the Friedmann and Hagen's quantum mechanical derivation of the
Wallis formula for $\pi$. In particular, we demonstrate that not only the
Gaussian trial function, used by Friedmann and Hagen, but also the Lorentz
trial function can be used to get the Wallis formula. The anatomy of the
integrals leading to the appearance of the Wallis ratio is carefully revealed.
