1Thomas Cooper to Thomas Jefferson, 1 September 1820 (Jefferson Papers)
pendulum; as basis for system of weights and measures [index entry]
2Thomas Jefferson to John Quincy Adams, 1 November 1817 (Jefferson Papers)
pendulum; as basis for system of weights and measures [index entry]
3T. H. Pasley to Thomas Jefferson, 12 August 1816 (Jefferson Papers)
pendulum; as basis for system of weights and measures [index entry]
4Robert Patterson to Thomas Jefferson, 10 January 1812 (Jefferson Papers)
pendulum; as basis for system of weights and measures [index entry]
5Thomas Jefferson to Robert Patterson, 10 November 1811 (Jefferson Papers)
pendulum; as basis for system of weights and measures [index entry]
6Thomas Jefferson to Robert Patterson, 11 September 1811 (Jefferson Papers)
pendulum; as basis for system of weights and measures [index entry]