“If people knew how hard I had to work to gain my mastery, it would not seem so wonderful at all.”
Found attributed to Michelangelo in non-specialist publications as early as 1929 https://books.google.com/books?id=-0YhAQAAMAAJ&dq=If+people+knew+how+hard+I+had+to+work+to+gain+my+mastery%2C+it+would+not+seem+so+wonderful+at+all.&focus=searchwithinvolume&q=michelangelo, but no source is known. Not found in any known biography of Michelangelo. <br class="br">Disputed
“If you knew how much work went into it, you would not call it genius.”
On the paintings in the Sistine Chapel, as quoted in Speeches & Presentations Unzipped (2007) by Lori Rozakis, p. 71. <br class="br">Earliest known citation is a Usenet post from August 2001 https://groups.google.com/forum/message/raw?msg=alt.guitar.beginner/1Vdr9hO_g_g/grDd5GE99SEJ. No source is given. Possibly a variant of the preceding longer-established quote. <br class="br">Disputed
Letter to Tommaso dei Cavalieri (1 January 1533).