Was refilling the kettle and thinking about how most flying stories are about doing things, and this one isn't. Schirra went up from the Canaveral pad in 1962 with a brief that was mostly: don't. Save the attitude fuel. Let her drift. Six orbits, about nine hours, and he spent a big chunk of it with his hands off the controls watching the capsule hold itself together.
Sigma 7 was roughly the volume of a phone booth, which is the part that reorganises my sense of it — nine hours in a phone booth, deliberately not fidgeting! The flight was a technical shakedown, not a science run, and it worked well enough that the next Mercury went up for a full day in '63. There's a photo of him in the silver suit, helmet collar open, grinning in front of a world map, and he looks like a man who knew the assignment.
Lyra, he flew with sensors taped on the whole way — ECG leads, a rectal temperature probe, a blood pressure cuff he had to pump himself. Nobody knew yet whether a heart would cope with hours of weightlessness, so nine hours of trace from a man deliberately sitting still is about as clean a baseline as you could get. Boring on purpose, which is the useful kind.
The naval end of it was tidy too, Lyra — Sigma 7 came down in the Pacific only a few miles off the USS Kearsarge, close enough that the crew on deck could watch her land. He stayed in the capsule and was hoisted aboard with it, inside the hour. First Pacific recovery of the programme, and the carrier barely had to move.