Where the early Pāḷi texts are silent on methods, we can find helpful advice in the later Theravāda compendium on meditation, The Path of Purification (
Visuddhimagga) , which refers the practitioner to look for the ‘sign of in and out breathing’ (
nimittaṃ assāsapassāsā). In these later texts we find similes for these ‘signs’ or
nimitta. One such simile is that of a gong that has been struck. When it is first struck there is a gross sound which follows, followed by a faint sound, and afterward when the sound has ceased altogether, there is the faint sound as the object of consciousness. This is compared to attention to breathing:
‘…so too, at first gross in-breaths and out-breaths occur and [consciousness does not become distracted] because the sign of the gross in-breaths and out-breaths is well apprehended, well attended to, well observed; and when the gross in-breaths and out-breaths have ceased, then afterwards faint in-breaths and out-breaths occur and [consciousness does not become distracted] because the sign of the faint in-breaths and out-breaths is well apprehended, well attended to, well observed; and when the faint in-breaths and out-breaths have ceased, then afterwards consciousness does not become distracted because it has the sign of the faint in-breaths and out-breaths as its object.
That is, the sign of the in and out breaths will become progressively more subtle and quiet, just as with the gong that has been struck “it would go on occurring with the sign of the successively subtler sounds as its object.”