According to Antaiji's website:
At one point he had a day off and decided to do zazen in his own room. By chance, an old parishioner who helped out at the temple entered the room and bowed towards him respectfully as if he were the Buddha himself. This old woman usually just ordered him around like an errand boy, so what was it that moved her to bow towards him with such respect? This was the first time that Sawaki Rōshi realized what noble dignity was inherent in the zazen posture, and he resolved to practice zazen for the rest of his life. In his old age, Sawaki Rōshi often said that he was a man who had wasted his entire life with zazen. The point of departure for this way of life lay in this early event.
He was eventually ordained, but his practice was interrupted by his required seven years of army service during the Russo-Japanese War. On returning to civilian life he practiced at Horyu-ji in Nara, one of the oldest Buddhist temples in Japan and a head temple of the Hosso-shu or Yogacara sect. He became thoroughly familiar with Yogacara teachings, studied Dogen and practiced zazen there until he moved on to teach at a local Sotoshu training temple. However, he was dismayed to find that neither teachers nor students practiced zazen seriously; the students were there to learn the ceremonies and rituals necessary to become temple priests. Again he moved on.
When he established practice in a borrowed temple, Sawaki Roshi's emphasis was on zazen. He and his students held monthly sesshin, during which they sat 50-minute zazen periods from 2 am to midnight, with three meal breaks. From midnight to 2 am, no one carried the kyosaku and practitioners could sleep for those two hours sitting there on their cushions.
Like his teacher before him, Kosho Uchiyama's focus was on zazen, knowing those who wanted to learn ceremonies had other places in which to learn them. While sesshin in other temples included liturgy, formal meals with chanting, lectures from teachers, work periods, teatime and other activities, Uchiyama Roshi continued his teacher's simple style, feeling that practitioners tended to turn these things into distractions from sitting. He called this approach "sesshin without toys."
He had spent three years sitting sesshin with his teacher in his strict style but after Sawaki Roshi's death Uchiyama Roshi made modifications that are still the norm at Sanshin today. For instance, he abandoned the use of the kyosaku, observing that when someone was walking behind the monks carrying the kyosaku, the ones sitting and the one walking around entered into a silent dialogue. This became a hindrance to really just sitting.
Uchiyama Roshi also decided that human beings need a certain amount of sleep in order to maintain mental health, so his sesshin schedule allowed for 7 hours of rest rather than two hours' dozing on the cushion. Under this schedule, he said, there was no excuse for sleeping during zazen. He did not change the 50-minute zazen and 10-minute kinhin periods, and these still make up the pattern of practice at Sanshin.
Sanshin continues the focus on zazen even though it offers a certain amount of dharma study. According to Okumura Roshi, studying Buddhism only as a scholar, without engaging in practice and living in Buddha's way, is like studying recipes without cooking or eating. Like Sawaki Roshi, he teaches that we have to wholeheartedly encounter our lives to find the meaning in them.