Yeah, that was a dumb mistake.
His work was "View of the Constitution of the United States".
http://oll.libertyfund.org/?option=com_staticxt&staticfile=show.php%3Ftitle=693&chapter=68851&layout=html#a_1661360
There is also this citation from James Kent
"The Constitution requires (a) that the President shall be a natural-born citizen, or a citizen of the United States at the time of the adoption of the Constitution, and that he shall have attained to the age of thirty-five years, and shall have been fourteen years a resident within the United States. Considering the greatness of the trust, and that this department is the ultimately efficient executive power in government, these restrictions will not appear altogether useless or unimportant. As the President is required to be a native citizen of the United States, ambitious foreigners cannot intrigue for the office, and the qualification of birth cuts off all those inducements from abroad to corruption, negotiation, and war, which have frequently and fatally harassed the elective monarchies of Germany and Poland, as well as the pontificate at Rome."
http://www.lonang.com/exlibris/kent/kent-13.htm
Not to worry.....been there.......done that!
There is also this citation from James Kent
"The Constitution requires (a) that the President shall be a natural-born citizen, or a citizen of the United States at the time of the adoption of the Constitution, and that he shall have attained to the age of thirty-five years, and shall have been fourteen years a resident within the United States.
And your original question:
“That provision in the constitution which requires that the president shall be a native-born citizen (unless he were a citizen of the United States when the constitution was adopted,) is a happy means of security against foreign influence, which, wherever it is capable of being exerted, is to be dreaded more than the plague.”
He erred as the wording in [Article II, Section I] of the Constitution does not say "Native Born. It says "Natural Born".....and there's a difference.
The reason that wording in the Constitution exists is simply because at the time of the signing of the Constitution there were no "Natural Born" Citizens available to serve as "Commander in Chief". Many of the colonists had been born in the colonies and many of their parents had also been born there as well...........but, they were all born as British subjects.
The framers, in essence had grandfathered any future "Native Citizens") from serving as the "Commander in Chief" because as time went on....there would eventually be no more "Citizens" (at the time of the signing of this Constitution) because they would soon die off. But in the meantime....at least for the next 30 or 40 years..... they did not want to disqualify themselves from serving as the "Commander in Chief".....just "Native Born" citizens who would come along later....i.e., born in the country of non citizen parents.
This section of the Constitution (Article I Section II] is direct proof that there indeed exists a difference between "Natural Born" and "Native Born" citizen. The third type of citizen the Constitution deals with is found in the "Naturalization clause" [Article I Section III]. That would be the person not born in the territorial limits of the country....but who immigrates and later decides to seek citizenship.