The Fourth of July, 1826
[When Asked by Mrs. Clark if he knew what day it was.]
JOHN ADAMS: “Oh, yes; it is the glorious Fourth of July.
It is a great day. It is a good day. God bless it. God bless you all.”
[He then lapsed into unconsciousness. He awakened later, and mumbled]
“Thomas Jefferson….”
[This is often reported as the beginning of the sentence
“Thomas Jefferson still survives.”]

But Jefferson had died a few hours earlier at the age of 82.

Close friends, then bitter enemies, but reconciled in later years, Adams and Jefferson both left this world on the 50th anniversary of their signing of the Declaration of Independence.

We also know they were both contemplating Don Quixote in the years prior to signing the Declaration: “Another child, Thomas Boylston, was born September of 1772, and again Adams was off on the ‘vagabond life’ of the circuit, carrying a copy of Don Quixote in his saddle bag…”
– John Adams by David McCullough, (another winner of the Pulitzer)

“Don Quixote was one of the few works of fiction that Thomas Jefferson was clearly partial to. He used the text in its original language to learn Spanish, and had his children do the same. Jefferson owned a number of different editions over his lifetime.”
– The Thomas Jefferson Encyclopedia at Monticello.org.
Also listed there are 18 pieces of Jefferson’s personal correspondence in
which Quixote is mentioned, spanning the 51 years from 1771 to 1822.