About This Answer
How deep must samādhi (concentration) be before contemplating the repulsiveness of the body? Ajahn Dtun answers that upacāra samādhi, access or neighbourhood concentration, is a firm enough basis. Some people have a natural aptitude for concentration and can go deeper; on withdrawing from that deeper state, they may see things even more clearly.
He compares the two levels with a sharpened knife used to cut a branch. With access concentration, one may need to strike up to three times before the branch breaks. With appanā samādhi, absorption, the knife is so sharp that a single stroke may be enough.