Albert EINSTEIN (1879-1955). P.A., [February 1926] 1 page oblong in-4, on an envelope of his own paper addressed on League of Nations letterhead. Autograph calculations, on an envelope addressed to 'Professor Einstein, 5, Haberlandstrasse, Berlin', posted to the League of Nations in Geneva on 26 February 1926, with the League of Nations stamp. Einstein used this envelope to write down a dozen or so algebraic calculations and equations with a neat, fine pen.