Albert Einstein's bold assertion of the form-invariance of the equation of a spherical light wave with respect to inertial frames of reference (Einstein 1905) became, in the space of six years, the preferred foundation of his theory of relativity. Early on, however, Einstein's universal light-sphere invariance was challenged on epistemological grounds by Henri Poincaré, who promoted an alternative demonstration of the foundations of relativity theory based on the notion of a light ellipsoid. A third figure of light, Hermann Minkowski's lightcone also provided a new means of envisioning the foundations of relativity. Drawing in part on archival sources, this paper shows how an informal, international group of physicists, mathematicians, and engineers, including Einstein, Paul Langevin, Poincaré, Hermann Minkowski, Ebenezer Cunningham, Harry Bateman, Otto Berg, Max Planck, Max Laue, A. A. Robb, and Ludwig Silberstein, employed figures of light during the formative years of relativity theory in their discovery of the salient features of the relativistic worldview.It is amazing how these historians jump thru hoops to credit Einstein.
Einstein's 1905 paper does say that light rays are preserved by Lorentz transformations, but Poincare's 1905 paper has the more general statement that the Lorentz metric is preserved. This is more general, because the light rays are those with a Lorentz metric of zero.
Acceptance of relativity theory, according to the best historical accounts, was not a simple function of having read Einstein’s paper on the subject.1 A detailed understanding of the elements that turned Einsteinian relativity into a more viable alternative than its rivals is, however, not yet at hand. ...This is a very strange way of saying it, but Einstein's 1905 was not widely accepted, and was not turned into a more viable alternative than its rivals. One of those rivals was Minkowski's 4D spacetime theory, and that is what achieved wide acceptance.
Planck also praised Hermann Minkowski’s four-dimensional approach to relativity, the introduction of which marked a turning-point in the history of relativity (Walter 1999a).
Poincare (1905b) was quick to grasp the idea that the principle of relativity could be expressed mathematically by transformations that form a group. This fact had several immediate consequences for Poincare’s understanding of relativity.This credits Poincare with understanding some aspects of relativity, but suggests that he was merely learning the work of others.
In fact, Poincare was the one who convinced Lorentz and Einstein of the principle of relativity. Poincare believed it and publicly promoted it when no one else did. And Poincare was the first to discover and publish that the transformations form a group. Today we call it the "Lorentz group" because Poincare did.
And of course he ends by trying to overcredit Einstein again:
Closely related to Einstein’s belief, the derivation of the Lorentz transformation via covariance of the light-sphere equation stabilized interpretations of the transformation along Einsteinian lines, and contributed powerfully to the emergence of a unified doctrine of the physics of inertial frames. One consequence of this movement was a heightened recognition of Einstein as the principal architect of the theory of relativity, as expressed by Laue’s 1911 treatise and its six re-editions.Walter reads the original papers, so he must know better than this. Lorentz covariance was discovered by Poincare and developed and popularized by Minkowski. Neither paid any attention to Einstein, and it is not even clear that Einstein understood the concept. Nobody got the concept from Einstein.
BTW, the author's name is Scott Walter, and he credits Poincare's Science and Hypothesis book as being published by Walter Scott. What's the deal with that? Is that some sort of Easter Egg joke inserted at the end of the paper just to see if we read it to the end?