The paper entitled "A nyugalmi nyomas tenyezoje" (The coefficient of pressure at rest) of Dr. Jozsef Jaky (1944) is perhaps one of the most cited in geotechnical engineering due to the importance of its still relevant proposals for solving any geotechnical problem. However, in a significant number of documents references to original article are generally limited to a simplified equation for calculating the k(0). As the original article by Dr. Jaky was published in Hungarian, it is common to find references that are unaware that the method proposed to determine k(0) is analytical and not empirical, and that it is applicable to granular materials of any type, including cereals. The present paper presents a rigorous version of the original article by Dr. Jaky, unambiguously presenting the formulations and the limits of validity behind the widely-known Jaky's Law.