“And I… at the close of (instructional discourse), steady, calm, make one-pointed and concentrate my mind subjectively in that first characteristic of concentration in which I ever constantly abide.”
(MN I 249, Pali Text Society vol I p 303)
Gautama’s statement implies that he did not experience “that first characteristic of concentration” when he spoke.
“That first characteristic of concentration” is “one-pointedness of mind”, as here in Gautama’s description of “right concentration”:
“And what… is the (noble) right concentration with the causal associations, with the accompaniments? It is right view, right purpose, right speech, right action, right mode of livelihood, right endeavor, right mindfulness. Whatever one-pointedness of mind is accompanied by these seven components , this… is called the (noble) right concentration with the causal associations and the accompaniments.”
(MN III 71, Pali Text Society vol III p 114; similar at SN V 17; “noble” substituted for Ariyan)
Even though giving “instructional discourse” meant the loss of “that first characteristic of concentration”, Gautama went ahead and taught, and he expected the monks in his order to do the same. He severely chastised a group of monks who had taken a vow of silence for their rainy-season retreat, and made a rule against the practice:
“Monks, an observance of members of other sects, the practice of silence, should not be observed. Whoever should observe it, there is an offence of wrong-doing.”
(2nd book of the Theravadin Vinaya, Khandhaka 4.1.13)
I have described the experience of “one-pointedness of mind” as the experience of the placement of attention by the movement of breath. I would contend that the necessity of breath utilizes the placement of attention to coordinate activity all the time, but consciousness of the placement enables the experience of a singularity in the location of attention from moment to moment:
The presence of mind can utilize the location of attention to maintain the balance of the body and coordinate activity in the movement of breath, without a particularly conscious effort to do so. There can also come a moment when the movement of breath necessitates the placement of attention at a certain location in the body, or at a series of locations, with the ability to remain awake as the location of attention shifts retained through the exercise of presence.
Gautama recommended that his followers “develop mindfulness of death”. He said that those who correctly practice “mindfulness of death” apply his teachings for the interval that it takes to “munch and swallow one morsel”, or for the interval that it takes to “breathe in and out, or out and in”*. The moments that Gautama cites are the moments where the movement of breath may stop momentarily, or seem to stop, and yet “one-pointedness of mind” is presumably still possible.
Moreover, the moments that he pointed to as the moments to practice his teaching (in order to be mindful of death) are precisely the moments crucial to the continuity of “one-pointedness of mind”.
*Maranassati Sutta, AN 6.19, Pali Text Society vol III p 218