1Thomas Jefferson to John Quincy Adams, 1 November 1817 (Jefferson Papers)
pendulum; as basis for system of weights and measures [index entry]
2Thomas Jefferson to Robert Patterson, 10 November 1811 (Jefferson Papers)
pendulum; as basis for system of weights and measures [index entry]
3Thomas Jefferson to Robert Patterson, 11 September 1811 (Jefferson Papers)
pendulum; as basis for system of weights and measures [index entry]