Almost all the construction steps described in the Head of a Man can be found in a small pen drawing of a head of Christ in the collection of the Albertina in Vienna.
A quadratic net can be ‘constructed’ for dividing the sections of the face. Diagonals drawn into it pass exactly along the corners of the mouth and lower sides of both eyes.
Divisions into strips can be placed above the eye and mouth zones, all equidistances are repeated and the radius of the inner construction circle reaches the corners of the eyes and mouth.
The equilateral triangle connects the eyes and tip of the nose and even the diagonals between chin and crown of the head intersect in the eyes.
Dürer was surely drawing on representations of Christ by German Old Masters such as Martin Schongauer or the Master E.S. The artists also assembled the countenance of Christ with similar strategies, according to rules (see The Harmonious Proportions of Christ).