I remember once reading the following: "This would have been
shorter,if I'd had more time" or words to that effect. I believe it
was Mark Twain, but am not sure. The remark clearly refers to the
difficulty of paring down long-winded prose to its essential meat.

Hello Nautico,

The source of this quotation is Blaise Pascal, Lettres Provinciales, 1657.

Blaise Pascal, Lettres Provinciales, 1657: 

"Je n'ai fait celle-ci plus longue que parce que je n'ai pas eu le
loisir de la faire plus courte." (I have made this [letter] longer
because I did not have the leisure to make it shorter.)
http://www.istori.com/cgi-bin/wiki?Quotations

Je n'ai fait celle-ci plus longue que parce que je n'ai pas eu le
loisir de la faire plus courte. (I have made this letter so long only
because I did not have the leisure to make it shorter.) ? Blaise
Pascal (Lettres Provinciales)
http://keithdevens.com/quotes/Pascal.shorter

Search strategy:

I found a very similar phrase on page 264 in the book The Life of His
Royal Highness the Prince Consort, Volume 5  by Theodore Martin.

?I will now make an end of my dissertation and set you free, but I
could not make  it shorter.  If I had had more time, I should have
been shorter," said Mr. Fox after making a long speech, and many are
the men who have the same tale to tell.?

http://books.google.com/books?vid=ISBN1402176236&id=cyzE_s9-puEC&pg=RA15-PA264&lpg=RA15-PA264&dq=%22+been+shorter%22++%22more+time%22&sig=G26HUYtmrbFyqcK-nhLk-k2bIbQ

This book was originally published in 1880
http://books.google.com/books?vid=ISBN1402176236&id=cyzE_s9-puEC&printsec=copyright&dq=%22+been+shorter%22++%22more+time%22

A footnote from the book

?Mr. Fox only said what had been often said before. Probably he took
the idea from Pascal, in the sixteenth of his Provincial letters. ?Je
n?ai fait celle-ci plus longue que parce que je n?ai pas eu le loisir
de la faire plus courte.?
http://books.google.com/books?vid=ISBN1402176236&id=cyzE_s9-puEC&pg=RA15-PA265&lpg=RA15-PA264&dq=%22+been+shorter%22++%22more+time%22&sig=0fi2gVlg8U-E8WHdHrH8IYMC2IU


I hope the information provided is helpful!

Best regards,
Bobbie7

Great answer. I'm glad I wasn't dreaming about Twain having said the same thing!

Great work Bobbie!  It might be interesting to note that Blaise Pascal is
-the- Pascal, as in "Pascal's law" and much more.  A phenomenal person
that accomplished an amazing body of work in just 39 years.

Blaise Pascal- From Wikipedia, the free encyclopedia.
http://en.wikipedia.org/wiki/Blaise_Pascal

Certainly can't argue with that, but I agree with Nautico's
recollection that Mark Twain expressed the same idea when someone
asked how much it would cost to have him speak on a subject.  When the
person heard his price and said that the group only wanted a short
speech, Twain replied that for a short speech the price would be
higher.

Ha, here it is.  I must have got the story wrong, or MT expressed a
similar sentiment in that context.
I trust the reference to NY Times is support enough:

http://neo-neocon.blogspot.com/2006/02/mark-twain-had-same-problem-i-do.html
http://www.nytimes.com/2006/02/12/weekinreview/12word.html?ei=5090&en=880efbcdfb77da7e&ex=1297400400&adxnnl=1&partner=rssuserland&emc=rss&adxnnlx=1157192222-yZnjJsUS+MO/ztSs1YNuGg

The latter only as verification of the NYT source.
It was most delightful searching through his speeches, but that was
the wrong way to find this.

Cheers, Myoarin

Nautico,

Thank you very much for the five stars and generous tip!

Bobbie7