I remembered this slightly differently, but when I looked up the author I found the original words, so I give them here.
Hence no force however great
Can stretch a cord however fine
Into a horizontal line
Which is accurately straight
—William Whewell, An Elementary Treatise of Mechanics, 1st Edition, 1819.
(For comparison, my memory of it was
There is no force, however great
Can pull a line, however fine
Into a horizonal line
That shall be absolutely straight
But I shall now try to remember the original version, since the fact is was a found poem is part of the charm. Changing the words loses that.)