Brahma Sutras
ॐ आ प्रायणात्तत्रापि हि दृष्टम् ॐ ॥ ४-१-१२॥
(Meditation is to be repeated) up till the moment of death, for it is noticed in the scriptures that it is done so even then.
english translation
OM A prAyaNAttatrApi hi dRSTam OM ॥ 4-1-12॥
hk transliteration by Sanscript