  We discuss the problems (and the promise) of the ingenious method introduced
by Lakes, and recently improved on by Luo, to detect a possible small photon
mass $\mu$ by measuring the ambient magnetic vector potential from large scale
magnetic fields. We also point out how an improved ``indirect'' limit can be
obtained using modern measurements of astrophysical magnetic fields and plasmas
and that a good ``direct'' limit exists using properties of the solar wind.
