“It is almost impossible to judge Mahler’s age from his face. One moment it seems as youthful as a boy’s; the next, it’s furrowed and aged far beyond his years.
“In the same way, his whole appearance can change from one extreme to the other within a few days, even a few hours. Sometimes he looks full in the face, sometimes strained and haggard.
“This all depends on the perpetual and swift transformations of his whole spiritual and physical nature. Each transformation possesses him completely, spontaneously, and with utmost intensity.”
— Natalie Bauer-Lechner, a close friend and intimate confidant