To General Soult commanding the camp at St Omer
La Malmaison 13 Feb 1804
"Make the skipper speak, and I even give you authority to promise him his pardon if he gives information; and if he should seem to hesitate you can go so far as to follow the custom as to men suspected of being spies, and squeeze his thumbs in the hammer of a musket."

Source of your quote, please?

Susan