According to Bohr's later report [1], at the 1930 Solvay conference Einstein made a final attempt at demonstrating that the actual possibilities of measurement and prediction, as allowed by quantum mechanics itself, lead to violations of the uncertainty relations. If this were correct, the conclusion would be inevitable that quantum mechanics is incomplete: a more precise description would be possible for an individual system than given by the quantum mechanical state. According to Bohr Einstein devised a thought-experiment with which it would be possible to predict both the precise energy of a photon and its exact time of arrival at a detector, in conflict with a version of the energy-time uncertainty relation. Bohr countered the proposal by arguing that if the details of the measuring procedure are properly considered, taking into account the quantum mechanical character of the measuring device itself, it turns out that the photon energy and the instant of the photon's emission from the source (a "photon box") cannot both be perfectly fixed.