In one of her best essays, “History by the Ounce,” published in Harper’s back in July 1965, Barbara Tuchman talks about the role of characteristic detail in providing an historical account. William Howard Taft, an American president who came to embody the age of excess, weighed in excess of 300 pounds. But how could this be effectively transmitted in a piece about Taft? That requires what she called the “corroborating detail.” She furnishes an example. One day, following an illness, Taft went out for a ride on his horse. He telegraphed Elihu Root saying he was “feeling fine.” To which Root promptly replied, “How is the horse feeling?”

Today Robert Windrem, writing in the Daily Beast, furnishes what will eventually emerge as an essential corroborating detail of the Bush program of “enhanced interrogation techniques.” The question is simple: how many bottles does it take to waterboard a prisoner?

In administering the Bush White House’s most infamous “enhanced interrogation” procedure, waterboarding, CIA questioners employed a civilized tool for a brutal task—bottled water, sometimes straight from the fridge. Current and former intelligence officials and testimony of two suspects themselves reveal this detail, one of many that help clarify how detainees underwent this procedure. A leading Bush administration official, retired Col. Lawrence Wilkerson, former chief of staff to Secretary of State Colin Powell, says that the numbers associated with CIA waterboarding sessions—such as 183 times for 9/11 mastermind Khalid Sheikh Mohammed and 83 times for al Qaeda training camp commander Abu Zubaydah—may even reflect the number of water bottles expended.

Apparently, four or five bottles were used per session. Wilkerson credits the information to a report from the Red Cross, but we can trace it back to Jay Bybee’s memorandums and those of his colleagues at the Justice Department’s Office of Legal Counsel, who paid close attention to the volume and flow of water used in the waterboarding process.

And there is another “corroborating detail” in Windrem’s story. Some of the bottles used had labels with an email address ending in “.pl,” suggesting that they were Polish waterbottles. That could mean that waterboarding was carried out in Poland, a fact which may prove of strong interest to criminal investigators in Poland now looking into charges that prisoners were tortured at one or more black sites maintained by the CIA on Polish soil.