Heart-to-Heart Talks with Philistines by the Pastor of His Flock http://books.google.com/books?id=4k8LAQAAIAAJ&q=%22we+are+moving+so+fast+that+when+plans+are+being+made+to+perform+some+great+feat+these+plans+are+broken+into+by+a+youth+who+enters+and+says+I+have+done+it%22&pg=PA178#v=onepage, The Philistine magazine, May 1913
As quoted in The Treasury of Humorous Quotations (1951) by Evan Esar, p. 103
As quoted in More Random Walks In Science : An Anthology (1982) by Robert L. Weber, p. 109.
Variante: The world is moving so fast these days that the man who says it can't be done is generally interrupted by someone doing it.
Variante: In these days, a man who says a thing cannot be done is quite apt to be interrupted by some idiot doing it.