In the early days of the Senate Filibuster, a senator could hold the floor (and halt all actions) as long as he could continue to speak or 3/5 of the Senate voted to end the filibuster. The filibuster imposed a physical burden on the Senator who chose to use it. Likewise, the other Senators had to be present in sufficient numbers to have a quorum, else the Filibusterer would be able to rest at he did not have to continue to speak if there was not a quorum. The Senate rules were changed to allow a Senator to “announce” a filibuster of a bill, and all action on that bill would stop but there was no burden on the filibustering senator or other senators who had to form the quorum. But in the 112th Congress, the Republicans resorted to more filibusters than there had been in the entire previous history of the Senate and Nelson wanted to return to the old requirement of holding the floor physically.