A gold pot of manna. The manna was preserved by divine power since it was normally perishable enough to breed worms and stink within 24 hours. The pot of manna was an uncomfortable reminder that despite what God had provided for them, the Israelites had rejected God’s provision.
Two tablets of stone on which were written the sum of the whole law-The Ten Commandments-called the "Testimony" because it "testifies" of God's revelation.
Aaron's rod that budded, to be kept as a token against the mumerings of the rebellious.