To complement medica's answer, and because I love trivia, I offer the following.
The original quote (in the OP's question) now updated is
Build a better mousetrap, and they will beat a path to your door
the popular advice is attributed to Ralph Waldo Emerson, but it was in 1889 that Sarah Yule included it in her book (p. 138 ), Borrowings, seven years after Emerson's death in April 27, 1882. In 1912 Yule stated she had copied it from a lecture delivered by the eminent American essayist in 1871. But there is no proof that he actually wrote those lines using the present subjunctive. A considerably longer version exists in Emerson's journal entry dated 1855
I trust a good deal to common fame, as we all must. If a man has good
corn, or wood, or boards, or pigs, to sell, or can make better chairs
or knives, crucibles or church organs, than anybody else, you will
find a broad hard-beaten road to his house.
Note that Emerson used the present indicative in this instance.
sources: What They Didn't Say: A Book of Misquotations by Elizabeth Knowles. Bartleby.com and Wikipedia