Tenn. Code Ann. § 66-23-101

If the person executing the instrument is dead, or resides or is beyond the limits of the United States and its territories, the instrument may be proved for registration before any clerk of a court of record in any of the states or territories, or before a commissioner for Tennessee, appointed by the governor, in any such state or territory, or before a notary public of such state or territory, by two (2) subscribing witnesses, or, if one (1) of them is dead, then by the subscribing witness living, and proof of the handwriting of the deceased witness by two (2) persons acquainted with such person's handwriting.