Einstein and de Haas published two papers in April 1915 containing a description of the expected effect and the experimental results. In the paper "Experimental proof of the existence of Ampere's molecular currents" they described in details the experimental apparatus and the measurements performed. Their result for the ratio of the angular momentum of the sample to its magnetic moment (the authors called it λ λ ) was very close (within 3%) to the expected value of 2 m / e . It was realized later that their result with the quoted uncertainty of 10% was not consistent with the correct value which is close to m / e . Apparently, the authors underestimated the experimental uncertainties.