Helen Duprey Bullock began the introduction to her compilation of The Papers of Thomas Jefferson as follows:
ON June 23, 1826, Thomas Jefferson noted in his “Epistolary Record” the receipt of a letter from V. W. Southall.
Jefferson kept meticulous records of his correspondence as well as copies of his letters. His work is a treasure of information about the mind of Jefferson and the era which produced America.
As noted elsewhere, Jefferson died on July 4, 1826. Thus, his mind was active until near the end.