"The introduction of a ``luminiferous ether'' will prove to be
superfluous..."

See: http://www.fourmilab.ch/etexts/einstein/specrel/www/ >
ON THE ELECTRODYNAMICS OF MOVING BODIES
By A. Einstein > June 30, 1905 > > "It is known that -=- >
"Examples of this sort, together with the unsuccessful attempts to
discover any motion of the earth relatively to the "light medium",
suggest that the phenomena of electrodynamics as well as of
mechanics possess no properties corresponding to the idea of
absolute rest.
They suggest rather that, as has already been shown to the first
order of small quantities, the same laws of electrodynamics and
optics will be valid for all frames of reference for which the
equations of mechanics hold good.1 We will raise this conjecture
(the purport of which will hereafter be called the ``Principle
of Relativity'') to the status of a postulate, and also introduce
another postulate, which is only apparently irreconcilable with
the former, namely, that light is always propagated in [OTHERwise]
empty space with a definite velocity c which is independent of the
state of motion of the emitting body. These two postulates suffice
for the attainment of a simple and consistent theory of the
electrodynamics of moving bodies based on Maxwell's theory for
stationary bodies. The introduction of a "luminiferous ether" will
prove to be superfluous inasmuch as the view here to be developed
will not require an ``absolutely stationary space'' provided with
special properties, nor assign a velocity-vector to a point of
the [OTHERwise] empty space in which electromagnetic processes
take place. -- A. Einstein