The difference being that Planck knew what the reality was (we knew what the spectrum of the sun looked like), but with consciousness we don't really know what the reality is (there is no "spectrum" of the mind for us to match).
Maybe we're still searching for the right theory of consciousness to know what exactly we're trying to measure?
Umnn, Michelson–Morley and Maxwell equations were enough experimental evidence before Einstein. Einstein work was reconciling Mechanics to confirm with electromagnetism, and not the other way round.
EDIT: Not to say there isn't some physics theory developed independent of experiments. But relativity is not a good candidate.