He was directly involved in increasing the intensity of one technique chronicled in Solzhenytsen's "Gulag Archipalago." To recap the Soviet method:
"There is the method of simply compelling a prisoner to stand there. This can be arranged so that the accused stands only while being interrogated - because that, too, exhausts and breaks a person down. It can be set up in another way - so that the prisoner sits down during interrogation but is forced to stand up between interrogations. (A watch is set over him, and the guards see to it that he doesn't lean against the wall, and if he goes to sleep and falls over he is given a kick and straightened up.) Sometimes even one day of standing is enough to deprive a person of all his strength and to force him to testify to anything at all."
Here's what Rumsfeld wrote in response to news that inmates had been forced to stand for only four hours:
"I stand for 8-10 hours a day. Why is standing limited to 4 hours?"
Remember that after Abu Ghraib came out, the Rumsfeld line was that he was shocked by what he had seen. In fact, he had not only authorized but monitored some of the torture techniques perfected at Gitmo, including "long time standing," and transferred, by his order, via General Miller, to Abu Ghraib. In other words, he lied before the Congress. In his defense, he offered to resign in shame. Bush refused to accept the resignation.