In 1903 De Pretto published a paper entitled "Hypothesis of Aether in the Life of the Universe", in which he proposed (similar to Samuel Tolver Preston in 1875) that matter moving at the speed of light would have kinetic energy equal to mc2, based on his (erroneous) belief that mv2 represented the kinetic energy of a body moving at the speed v. He then speculated that ordinary matter may be considered to be moving at the speed c, agitated by an ultra-mundane flux. De Pretto's paper was later included in the proceedings of an Italian scientific institute. According to de Pretto, "the matter of any body contains within it a sum of energy represented by the entire mass of the body[... ] Nobody will easily admit that, stored in a latent state, in any kilogram of matter, completely hidden to all our investigations, hides such a sum of energy, equivalent to the amount that can be extracted from millions and millions of kilograms of coal." However, de Pretto's line of reasoning is not regarded as scientifically meaningful by the mainstream scientific community.
Although the idea of a relationship between mass and energy was not novel at the time de Pretto wrote, Umberto Bartocci, a former University of Perugia historian of mathematics and ardent opponent of Albert Einstein's theory of relativity, has argued that de Pretto should be credited as the originator of this idea, and that Einstein took the idea from de Pretto. However, Bartocci's views have not appeared in any scholarly journal. His efforts to popularize his views have been limited to articles in newspapers. Einstein's conception of mass-energy equivalence is dissimilar to de Pretto's, and Einstein's deduction of this equivalence from the theory of relativity bears no resemblance to de Pretto's (erroneous) reasoning.