Woldemar Voigt published in 1887 the article : “On Doppler’s Principle” which has unfortunately received little recognition by physicists and historians of physics [2–6]. Apparently, he was the first — or at least one of the firsts — who demanded form invariance of a physical law to obtain a set of transformation equations. This remarkable idea began the search for physical symmetries in field theories. More precisely, Voigt demanded form invariance of the homogeneous wave equation in inertial frames and obtained a set of spacetime transformations now known as the Voigt transformations ...Voigt's transformations were not exactly the same as the Lorentz ones, and he did not have some of the other essential relativity breakthrus of Lorentz and Poincare.
In the creation of special relativity, we traditionally find the names of Lorentz, Larmor, Poicar´e and Einstein. They appear to be the main actors. Voigt is relegated to being a minor player, in the best of cases. But this tradition is not faithful to the history of physics, since Voigt was the first in applying the two postulates of special relativity. He deserves a place in textbooks. The idea of demanding that the wave equation should not change its form when observed by different inertial frames, was the great conceptual contribution of Voigt, since it opened the gate to the world of physical symmetries. This is the legacy of Voigt’s 1887 paper.
Deducing symmetries from equations of physics became one of the great ideas of XX century physics. Voigt was a pioneer in 1887.