“Now it is certain.
There is no magic stone.
No secret to be found.
One must go
With the mind's winnowed learning.”

Source: Night Lamp (1996), Chapter 5, section 3 (p. 81)

Source: Eugene Onegin (1823), Ch. 1, st. 59.

À en croire certains esprits bornés, — c'est le qualificatif qui leur convient, — l'humanité serait renfermée dans un cercle de Popilius qu'elle ne saurait franchir, et condamnée à végéter sur ce globe sans jamais pouvoir s'élancer dans les espaces planétaires! Il n'en est rien! On va aller à la Lune, on ira aux planètes, on ira aux étoiles, comme on va aujourd'hui de Liverpool à New York, facilement, rapidement, sûrement, et l'océan atmosphérique sera bientôt traversé comme les océans de la Lune!
Tr. Walter James Miller (1978)
Variant: If we are to believe certain narrow minded people — and what else can we call them? — humanity is confined within a circle of Popilius from which there is no escape, condemned to vegetate upon this globe, never able to venture into interplanetary space! That's not so! We are going to the moon, we shall go to the planets, we shall travel to the stars just as today we go from Liverpool to New York, easily, rapidly, surely, and the oceans of space will be crossed like the seas of the moon.
Source: From the Earth to the Moon (1865), Ch. XIX: A Monster Meeting (Charles Scribner's Sons "Uniform Edition", 1890, p. 93)

“Five Thousand Years Later” (p. 749)
Seveneves (2015), Part Three

The Human Biocomputer (1974) <!-- London: Abacus -->
Context: In the province of the mind, what one believes to be true is true or becomes true, within certain limits to be found experientially and experimentally. These limits are further beliefs to be transcended. In the mind, there are no limits... In the province of connected minds, what the network believes to be true, either is true or becomes true within certain limits to be found experientially and experimentally. These limits are further beliefs to be transcended. In the network's mind there are no limits.

John Banville on the birth of his dark twin, Benjamin Black (2011)

" The Life and Teachings of Thoth Hermes Trismegistus http://magdelene.net/Thoth%20Hermes%20Trismegistus.htm", in The Secret Teachings of All Ages (1928) by the Canadian occultist Manly Hall; a few quotation websites credit this to Addison.
Misattributed

Source: Masquerade