http://memory.loc.gov/cgi-bin/ampage?collId=llcg&fileName=056/llcg056.db&recNum=474
I don't see anything there either to suggest that a large number of people thought in 1861 that the war would be a long one.
It's generally accepted that people on both sides thought that the other would yield without much fighting.
President Lincoln says in his second inaugural that no one anticiaptated the war's duration.
Walt
The original question was not long war/short war. It was war/no war and if Congress would be reconvened in the event of war.
As I stated earlier: "And as you well know, many in Congress rightfully believed that war was just around the corner and expected without any reason for doubt that they would be immediately reconvened if it broke out while they were away."
You asked for documentation of that fact. So I directed you to the special session of the senate in March 1861, where the issue of keeping congress informed of any military activities and reconvening it in the event of war came up on a regular basis.