Year	Author	Major points
1881	J. J. Thomson [7]	Proposed that a charged conductor in motion increases its mass by $\frac{4}{15} \frac{μ e^{2}}{a}$ , where μ is magnetic permeability, a is the radius of a charged sphere, e is the electric charge.
1889	O. Heaviside [8]	Simplified Thomson’s work and suggested that the effective mass is also proportional to $E / c^{2}$
1900	H. Poincare [9]	The relation of mass-energy equivalence $E = m c^{2}$ was first mentioned in this paper. It is in the form of $ρ = J / c^{2}$ , where ρ is the mass density, J is the energy density.
1901 1902	W. Kaufmann [17] [68]	Reported the first experimental results showing that electron’s mass varies with speed.
1902	M. Abraham [22]	His study suggested that the effective mass for an electron is $m = (4 / 3) E / c^{2}$ .
1904	H. A. Lorentz [10] [20]	Showed that the electron mass parallel to the direction of motion is $m_{L} = γ^{3} m$ and the mass perpendicular to the direction of motion is $m_{T} = γ m$ , where $γ = 1 / \sqrt{1 - v^{2} / c^{2}}$ .
1905a	A. Einstein [5]	Einstein published his famous paper on Special Relativity. He proposed that the mass of an “electron” is not constant. Based on Newton’s definition of mass, he derived his speed-dependence relations for longitudinal mass and transverse mass.
1905b	A. Einstein [25]	By proposing a thought experiment of an object sending out radiations in opposite directions, he concluded that “If a body gives off the energy L in the form of radiation, its mass diminishes by L/c².”
1906	A. Einstein [27] [29]	He proposed a thought experiment using a box with radiation waves transmitting inside. Based on conservation of center of gravity, he derived the mass-energy equivalence relation.
1907a	A. Einstein [28]	Proposed another thought experiment of a rigid body moving in an electric field. He showed that one can obtain $E_{0} = m c^{2}$ “from a standing point of relativistic electrodynamics”.
1907b	A. Einstein [70]	Proposed to extend the mass-energy equivalence relation to gravitational mass.
1908	M. Planck [71]	Proposed that the mass change in the absorption and emission of heat energy is $Δ m = E / c^{2}$ .
1909	A. Einstein [72]	Used the same thought experiment and argument proposed in 1905b paper to derive “the inertial mass of a body decreases by L/c² when the body emits the radiation energy L”. The derivation was made more simple and explicit.
1911	A. Einstein [73]	Proposed a thought experiment to show that an increase in gravitational mass is also E/c². This paper is also thought to be the author’s attempt to develop General Relativity.
1912	A. Einstein [74]	Proposed a thought experiment modified from the 1905b paper to derive the mass-energy equivalence relation. This time with a plate sending out two plane waves in opposite directions, and the plate was treated as a point mass.
1913	A. Einstein [75]	Proposed to prove the mass-energy equivalence relation using the stress-energy tensor based on electro-magnetic field considerations.
1922	A. Einstein [76]	Produced a more refined version of his energy-momentum tensor treatment for relativity. This was based on his Stafford Lectures delivered at Princeton during a visit in May 1921 [29] .
1935	A. Einstein [77]	Considered a system using two mass-points traveling toward each other. Based on the argument of conservation of momentum and conservation of energy, he concluded that one can regard $m c^{2} (γ - 1)$ as the kinetic energy of the particle.
1946	A. Einstein [38]	Einstein’s last effort to prove $E_{0} = m c^{2}$ . The text was short and simple. The treatment “does not presume the formal machinery of the theory of relativity, but uses only three previously known laws”: conservation of momentum, the equation for radiation pressure, and the expression for stellar aberration of light [29] .