Statistics for occurrence #1 of “Messrs. Mason” in chapter 4.16 of Robert Underwood Johnson, Clarence Clough Buell, Battles and Leaders of the Civil War: Volume 2.:

...nified and manifested no little indignation as he spoke of the unusual treatment received at our hands. I immediately asked if I might see his passenger-list, saying that I had information that Messrs. Mason and Slidell were on board. The mention of Mr. Slidell's name caused that gentleman to come up and say, I am Mr. Slidell; do you want to see me? Mr. Mason, whom I knew very well, also came up at ...
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