  Electric and magnetic Hertz potentials are a formalism for obtaining
solutions of Maxwell's equations from solutions of the inhomogeneous wave
equation, with polarisation and magnetisation as the sources. We provide an
overview of their covariant transformation properties, and examine an
application of Hertz potentials to the Lorentz transformation of localised
pulses by Lekner, who obtained a result seeming to contradict Von Laue's
theorem. We show that Lekner's result of total energy-momentum not transforming
as a four-vector was due to an erroneous transformation of Hertz potentials,
that did not take into account their bivector nature.
