A Thermarest, or even one of those blue foam groundpads, and a light sleeping bag and can be stowed discreetly in a filing cabinet.

There was a story going round at the old firm about one of the associates. He went through a divorce, and simply moved into his office. Kept a few suits and shirts on the back of his door, showered at the gym, got his laundry done at the cleaner's in his building, and slept under his desk. It was a year before this was noticed.

He apparently billed like a pig-dog and got into pretty good shape doing this.