George Washington adding "under God" to the Presidential oath

[Volokh, Eugene]

	I've heard various people mention that George Washington added
"so help me God" to the constitutionally prescribed, which is "I do
solemnly swear (or affirm) that I will faithfully execute the Office of
President of the United States, and will to the best of my Ability,
preserve, protect and defend the Constitution of the United States."
Some use it as evidence for the propriety of religious references in
government affairs; others stress that "so help me God" isn't actually a
part of the official oath, and the frequent inclusion of "so help me
God" is the Presidents' own detour and frolic.

	Here's my question:  In the late 1700s, did people who said
oaths (as opposed to affirmations) routinely include "so help me God" or
some such, simply because that was seen as a natural part of oaths?  If
so, then it might be that the Framers naturally expected that those who
see an oath as a religiously significant matter would include "so help
me God."

	Eugene