Straight from today’s Quotle — here’s who really said it, and the story behind it. Play again

Who really said it

Iron rusts from disuse; stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigor of the mind

Written by Leonardo da Vinci 1452–1519 · Florentine painter, engineer & polymath
Verified Free to reuse

Genuine, and unusually well documented for a Leonardo line. The exact English wording is Edward McCurdy’s translation of a note from Leonardo’s manuscripts, printed word for word on p. 51 of Leonardo da Vinci’s Note-Books, Arranged and Rendered into English, with McCurdy’s own marginal reference to the Codex Atlanticus, folio 289 verso.

Last verified 6 Aug 2026 · how we verify · spot an error?

For presentations

Put it on a slide

Verified quote & credit

“Iron rusts from disuse; stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigor of the mind” Leonardo da Vinci, Leonardo da Vinci's Note-Books, trans. Edward McCurdy (New York: Empire State Book Company, 1923), p. 51. Verified at Quotle.info · Verbatim: “Iron rusts from disuse; stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigour of the mind.”

Can you use it?

Free to use, including in commercial and paid presentations — no permission or licence needed.

Image direction — grounded in this quote’s real context; paste into your image tool

In context

Evoking the world of Leonardo da Vinci — Florentine painter, engineer & polymath. Theme: "Iron rusts from disuse; stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigor of the mind". Atmospheric and restrained, cinematic directional light, a muted period-appropriate palette, fine grain and texture. Compose with generous empty space for the quote and a small credit line. No lettering in the image itself.

Minimalist

Minimalist editorial slide for the quote "Iron rusts from disuse; stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigor of the mind". Clean background, a single muted accent color, generous negative space, subtle paper or linen texture, no literal illustration — let the words carry it. Reserve clear space for a serif quote and a small credit line. No lettering in the image itself.

Provenance

The page it sits on

Work
Leonardo da Vinci’s Note-Books, Arranged and Rendered into English with Introductions
Translation
Edward McCurdy; first published 1906. Text read here in the 1923 Empire State Book Company printing, New York.
Location
Book I, “Life” — page 51
Manuscript
McCurdy’s marginal reference: Codex Atlanticus, folio 289 verso

While I thought that I was learning how to live, I have been learning how to die. (C.A. 252 r. a.)

The age as it flies glides secretly and deceives one and another; nothing is more fleeting than the years, but he who sows virtue reaps honour. (C.A. 71 v. a.)

Iron rusts from disuse; stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigour of the mind. (C.A. 289 v.)

Life well spent is long. (Tr. Tav. 63 a.) Book I: Life — p. 51

The parenthetical tags are McCurdy’s own manuscript references; “C.A.” is the Codex Atlanticus. Spelling and punctuation follow the printed page, including the British “vigour.”

Read McCurdy's Note-Books in full at the Internet Archive

How we traced it

  • The exact sentence — semicolons and all — is on p. 51 of Edward McCurdy’s Leonardo da Vinci’s Note-Books, followed by his manuscript reference to the Codex Atlanticus, in the full scanned text ↗. The only difference from the version that circulates online is the British spelling “vigour.”
  • The copy examined is the 1923 Empire State Book Company printing ↗ (New York). Open Library ↗ dates McCurdy’s Note-Books to 1906 and lists the 1923 printing among its editions.
  • The rival Victorian translation reads nothing like it: Jean Paul Richter’s maxim no. 1177 gives “Just as iron rusts unless it is used, and water putrifies or, in cold, turns to ice, so our intellect spoils unless it is kept in use” — see Richter’s text at Project Gutenberg ↗.
  • An independently sourced collection reaches the same conclusion: Today in Science History ↗ credits the wording to McCurdy and repeats the manuscript reference “C.A. 289 v.”
Public domain

Leonardo’s Italian original has been in the public domain for centuries. The English wording quoted here is Edward McCurdy’s translation, first published in 1906 and read for this page in the 1923 Empire State Book Company printing — both well before the 1931 US cutoff, so the translation is in the public domain too. Later McCurdy editions from 1938–39 are separate publications and are not the text quoted here.

Rights status is our research, not legal advice — and copyright varies by country and edition. For commercial or published use, confirm with the rightsholder. See terms.

Fact-check

Right author, wrong book

The attribution to Leonardo holds up. What almost every quote site gets wrong is where the wording comes from — and a couple of mutated versions have broken loose along the way.

Jean Paul Richter’s edition of the Notebooks mis-cited

Wikiquote ↗ files this wording under Richter’s Notebooks, and aggregators such as LibQuotes ↗ copy that citation. But Richter’s translation renders the maxim — no. 1177, among his Philosophical Maxims — as “Just as iron rusts unless it is used, and water putrifies or, in cold, turns to ice, so our intellect spoils unless it is kept in use.” The familiar phrasing does not appear in Richter’s text ↗ at all.

“Just as iron rusts from disuse, even so does inaction spoil the intellect” hybrid variant

A shortened mashup circulated by sites such as Quotes.net ↗: it borrows McCurdy’s opening (“iron rusts from disuse”) and welds it onto Richter’s ending (“spoil the intellect”). It matches neither translation.

“sap the vigors of the mind” drifted plural

PassItOn ↗ prints the plural “vigors.” McCurdy’s text has the singular British “vigour.” The American respelling “vigor” is standard online and harmless; the plural is not in the source.

The note is Leonardo’s, from the Codex Atlanticus. The thirty English words everyone quotes are Edward McCurdy’s 1906 rendering, and they can be read on p. 51 of his Note-Books ↗.

Context

A note to himself, not a slogan

Leonardo did not write aphorisms for publication. These lines come from working notebooks — loose sheets of mirror-written Italian, mixed in among gear diagrams, shopping lists and anatomical studies — that were scattered after his death and only assembled into printed collections in the nineteenth and twentieth centuries. The maxim about rusting iron sits on a page of McCurdy’s arrangement surrounded by other notes on time and death: “Life well spent is long,” and “While I thought that I was learning how to live, I have been learning how to die.”

The reason this particular sentence sounds so quotable in English is that two rival translators made very different choices. Jean Paul Richter’s Victorian edition renders the same idea flatly — iron rusting “unless it is used,” the intellect spoiling “unless it is kept in use.” Edward McCurdy reached for the cadence that made it a poster: rusts from disuse… loses its purity… sap the vigour of the mind. The thought is Leonardo’s; the music is McCurdy’s.

The thought is Leonardo’s. The music is his 1906 translator’s.

Why the translator matters here

Quote sites almost universally credit this wording to “The Notebooks of Leonardo da Vinci, Richter.” That is checkable, and it does not check out: Richter’s translation renders the maxim as no. 1177 among his “Philosophical Maxims,” in wording that shares almost nothing with the famous version. Nobody reading Richter would come away with “sap the vigour of the mind.”

This is a useful reminder that with translated authors, attribution has two halves. Leonardo wrote the note. But if you are quoting these particular thirty words in English, you are quoting Edward McCurdy — which is why the translator belongs in the citation.

Explore

Filed under

More provenance-checked quotes on the same theme, each with its reuse status.

Work Growth

Go further

Dig deeper

Trusted places to keep pulling the thread — primary archives, fact-checks, and scholarship. We show how we used each one before you leave.

McCurdy's Note-Books — full textarchive.org

The complete scanned text of the 1923 Empire State Book Company printing. Search for “Iron rusts” — the sentence appears on p. 51 with McCurdy’s Codex Atlanticus reference.
Scan record for the 1923 printingarchive.org

Catalogue page for the digitised copy: Edward McCurdy, Empire State Book Company, New York, 1923.
Richter's Notebooks of Leonardo da Vincigutenberg.org

The rival Victorian translation. Maxim no. 1177 renders the same thought as “Just as iron rusts unless it is used…” — the famous wording is nowhere in it.
Leonardo da Vinci — Wikiquoteen.wikiquote.org

Carries the quote, but files it under Richter’s 1883 edition rather than McCurdy’s — the mis-citation most quote sites inherit.
Leonardo da Vinci science quotationstodayinsci.com

A sourced collection that correctly credits McCurdy and repeats the manuscript reference “C.A. 289 v.”
Open Library — Leonardo da Vinci's note-booksopenlibrary.org

Catalogue record dating McCurdy’s Note-Books to 1906, with the 1923 Empire State Book Company printing among its editions.

The true author

Leonardo da Vinci

Leonardo da Vinci

1452–1519 · Florentine painter, engineer & polymath

Leonardo was born 15 April 1452 near the Tuscan hill town of Vinci and died 2 May 1519 at Clos Lucé in Amboise, France. Wikipedia describes him as a painter, draughtsman, engineer, scientist, theorist, sculptor and architect of the High Renaissance — a range that explains why so many stray aphorisms get pinned on him. What makes this one different is that he left thousands of pages of private notebooks, written in mirror script, and translators have been able to point at the actual folio.

For writers & researchers

Cite this

Chicago

Leonardo da Vinci. Leonardo da Vinci’s Note-Books, Arranged and Rendered into English with Introductions. Translated by Edward McCurdy. New York: Empire State Book Company, 1923, p. 51. McCurdy’s rendering was first published in 1906. Leonardo’s marginal manuscript reference: Codex Atlanticus, fol. 289 verso.

This verification page

Quotle.info. “Who really said ‘Iron rusts from disuse; stagnant water loses its purity and in cold weather becomes frozen; even so does inaction sap the vigor of the mind’?” Last verified 6 Aug 2026. https://quotle.info/who-said/iron-rusts-from-disuse-stagnant-water-loses-its-purity-and/

Something wrong on this page?

Tell us what’s off. A link helps but isn’t required — “this is the wrong person” is a useful report on its own. Nothing here changes the page directly; it goes to our review queue and a human checks it.

Only used to tell you if we act on your report. We never sell or share it.

Copied