I only found out he’d done this after he died.

THE PANTHER
Jardin des Plantes, Paris

The bars go by, and watching them his sight
grows tired and fails to grasp what eyes are for.
There are a thousand bars, it seems to him;
behind the thousand bars there’s nothing more.

The supple gait of swift and powerful steps
pacing out its circle on the ground
is like a dance of strength around a center
in which a great bewildered mind is bound.
Yet now and then the curtain of the pupil
silently parts: a picture goes inside,
slips through the tightened limbs, and in the heart
ceases to be, like something that has died.

–Rainer Maria Rilke

Translated by my father from the German in 1967, overnight, after a request from a colleague.