摩訶止觀 2.19

2.19

意論止觀者，念西方阿彌陀佛，去此十萬億佛剎，在寶地、寶池、寶樹、寶堂、眾菩薩中央坐說經。三月常念佛。云何念？念三十二相，從足下千輻輪相，一一逆緣念諸相，乃至無見頂；亦應從頂相順緣，乃至千輻輪，令我亦逮是相。

Regarding mental discussion of calming and contemplation: contemplate Amitābha Buddha of the western direction, a hundred thousand koṭis of buddha-lands away from here, sitting and preaching the sūtra amidst jeweled ground, jeweled ponds, jeweled trees, jeweled halls, and a host of bodhisattvas. For three months, constantly contemplate the Buddha. How to contemplate? Contemplate the thirty-two marks: from the thousand-spoked wheel mark on the soles of the feet, reverse-trace and contemplate each mark up to the invisible cranial protuberance; one should also trace forward from the cranial protuberance down to the thousand-spoked wheels, wishing: "May I also attain these marks."