Two, three, five, seven, eleven, seventeen, nineteen, twenty-three, twenty-nine, thirty-one…in.
Thirty-seven, forty-one, forty-three, forty-seven, fifty-three, fifty-nine, sixty-one, sixty-seven, seventy-one, seventy-three…out.
Sherlock found simply counting seconds as they passed, breathing in and out, failed to calm his mind and reveal the center he sought. He counted by prime numbers instead, one per second, as he deliberately employed this otherwise autonomic system.
Seventy-nine, eighty-three, eighty-nine, ninety-seven, one-hundred-one, one-hundred-three, one-hundred-seven, one-hundred-nine, one-hundred-thirteen…
Eventually the exercise of calculating the primes – rather than repeating them through memorization – helped him achieve a meditative state.
The position of his body was important, too. His primary thinking position was a recumbent pose, perfect for expending minimal physical energy while maximizing resources available for mental effort. The position of his hands (pressed together from palm to finger-tip and positioned to rest just so against the cupid's bow of his lips) and arms (relaxed, bent at the elbows, shoulders moving down the back and elongating the spine) ensured he wouldn't relax so much physically as to lose himself in the recesses of his own mind.
He'd held the position once for three days, breaking only once to expel waste and rehydrate.
Sherlock was quite proud of the accomplishment.
John, though, hadn't been impressed.