No single known document definitively proves the maiden name of Mary Frizzle, wife of John Frizzle (c1718-1818). Rather, a plethora of strong circumstantial evidence suggests that Mary was the daughter of Jesse Rountree (born 1715-1725) and his wife Rachel (supposedly a Spivey, although I have no hard proof of Rachel's maiden name). Although not solid documentation, I believe this evidence leaves no doubt that John Frizzle’s wife Mary was Mary Rountree, daughter of Jesse and Rachel Spivey Rountree:
** In 1777, Jesse Rountree named his daughter Mary in his will, but did not give a surname for her. But also in his will, Jesse named his son John Rountree and John "frzle" as his executors. John Frizzle later appeared before the officials of the colony of North Carolina and agreed to be the executor; he also signed the inventory. Clearly, John Frizzle had a close connection to Jesse Rountree.
** John Frizzle witnessed a deed of Jesse Rountree’s in 1774
** John Frizzle and Jesse Rountree (Jr.) lived on adjoining plantations between 1789 and 1818.
** John and Mary Frizzle sold land to William Rountree, son of Jesse Rountree, Sr., on two occasions in 1779, and William Rountree witnessed one of John Frizzle’s deeds in 1781. William Rountree lived on a plantation adjoining that of John and Mary Frizzle’s between 1779 and 1789, when Rountree sold his plantation to his younger brother Jesse Rountree.
** Numerous Rountrees witnessed various deeds of John Frizzle’s in the 1700s, including Moab, Obed, Reuben, and Francis Rountree. They appear to have been nephews of the elder Jesse Rountree.
** Several grandsons and great-grandsons of Penelope Frizzle Albritton (daughter of John and Mary Frizzle) were named James Rountree Albritton or Jesse Rountree Albritton. ==================================
If you would like additional information on John Frizzle or Jesse Rountree, let me know and I'll share what I have on them.