There is a sentence in The Naval Treaty (one case included in The Memoirs of Sherlock Holmes by Sir Arthur Conan Doyle):
He had, when he so willed it, the utter immobility of countenance of a red Indian, and I could not gather from his appearance whether he was satisfied or not with the position of the case.
What does this sentence mean?
In addition to the definitions of the individual words, I feel a cultural reference is being made here as well. What did Watson (or rather, Doyle) mean by this sentence?