According to the Constitution Society, "The Law of Nations," a 1758 work by Swiss legal philosopher Emmerich de Vattel, "was read by many of the Founders of the United States of America and informed their understanding of the principles of law which became established in the Constitution of 1787."
Vattel writes in Book 1, Chapter 19, of his book, "The natives, or natural-born citizens, are those born in the country, of parents who are citizens. As the society cannot exist and perpetuate itself otherwise than by the children of the citizens, those children naturally follow the condition of their fathers, and succeed to all their rights. … In order to be of the country, it is necessary that a person be born of a father who is a citizen; for, if he is born there of a foreigner, it will be only the place of his birth, and not his country."
Five years later, however, Congress repealed the Act and never again drafted a legally binding definition of "natural born citizen."