“What is not ephemeral in individual life, if life itself is fleeting like a dream.”

In a Grove (1922), quoted in A Study Guide for Ryunosuke Akutagawa's "In a Grove" https://books.google.it/books?id=EAPQDAAAQBAJ&pg=PT13 (Gale, 2017).

¿Qué es la vida? Un frenesí.
¿Qué es la vida? Una ilusión,
una sombra, una ficción,
y el mayor bien es pequeño;
que toda la vida es sueño,
y los sueños, sueños son.
Variant:
What is this life? A frenzy, an illusion,
A shadow, a delirium, a fiction.
The greatest good's but little, and this life
Is but a dream, and dreams are only dreams.
(trans. Roy Campbell)
Segismundo, Act II, l. 1195.
La vida es sueño (Life is a Dream)

Source: Titus Groan

Source: The Dream of a Ridiculous Man (1877), V
Context: A dream! What is a dream? And is not our life a dream? I will say more. Suppose that this paradise will never come to pass (that I understand), yet I shall go on preaching it. And yet how simple it is: in one day, in one hour everything could be arranged at once! The chief thing is to love others like yourself, that's the chief thing, and that's everything; nothing else is wanted — you will find out at once how to arrange it all. And yet it's an old truth which has been told and retold a billion times — but it has not formed part of our lives! The consciousness of life is higher than life, the knowledge of the laws of happiness is higher than happiness — that is what one must contend against. And I shall. If only everyone wants it, it can be arranged at once.

The Novel of the Future (1969)

Source: Spiritual Journey: Michio Kushi's Guide to Endless Self-Realization and Freedom (1994, with Edward Esko), p. 64

With the century, vol. 8

Source: Cosmos