“It's only those who are persistent and willing to study things deeply, who achieve the master work.”

This quotation first appeared in Dreams Come Due: Government and Economics as if Freedom Mattered (New York: Simon & Schuster, 1986), p. 312, written under the pseudonym of John Galt. It is there attributed to Jefferson, but is not found anywhere in his works. See the Thomas Jefferson Encyclopedia http://www.monticello.org/site/jefferson/democracy-will-cease-to-exist-quotation.
Misattributed

Source: Giovanni's Room

Prose Observations (Oxford: 1979), p. 4

Source: A Short History Of The English Law (First Edition) (1912), Chapter IV, Improved Legal Procedure, p. 40

Source: Transcendental Magic: Its Doctrine and Ritual

Source: Initiation, The Perfecting of Man 1923, p. 148

In her preface to the book "Prieres et Meditations" which was translated into English by Sri Aurobindo, quoted in "Diary notes and Meeting with Sri Aurobindo."
Sayings