Landau kept a list of names of physicists which he ranked on a logarithmic scale of productivity ranging from 0 to 5. The highest ranking, 0, was assigned to Isaac Newton. Albert Einstein was ranked 0.5. A rank of 1 was awarded to the founding fathers of quantum mechanics, Niels Bohr, Werner Heisenberg, Satyendra Nath Bose, Paul Dirac and Erwin Schrödinger, and others, while members of rank of 5 were deemed "pathologists". Landau ranked himself as a 2.5 but later promoted to a 2. N. David Mermin, writing about Landau, referred to the scale, and ranked himself in the fourth division, in the article "My Life with Landau: Homage of a 4.5 to a 2".