[641] "Internally" (ajjhattaṃ): that which is internal, one's own (paccattaṃ).
"With a mind stilled" (vūpasantacitto): Herein, what is mind (citta)? That which is mind, mentation (mano), mentality (mānasa) … the corresponding mind-consciousness element (tajjā manoviññāṇadhātu) — this is called mind. This mind is internally calm (santa), quieted (samita), stilled (vūpasanta); therefore it is said: "with a mind stilled internally" (ajjhattaṃ vūpasantacitto).
English translation from the Pali (Siam Raṭṭha edition) — under review, not for citation.