Visuddhimagga III-14

Samādhicatukkavaṇṇanā

Catukkesu paṭhamacatukke atthi samādhi dukkhāpaṭipado dandhābhiñño, atthi dukkhāpaṭipado khippābhiñño, atthi sukhāpaṭipado dandhābhiñño, atthi sukhāpaṭipado khippābhiññoti.

（四）（四法）六种之中：（1）（苦行道迟通达、苦行道速通达、乐行道迟通达、乐行道速通达）于第一种四法：即为定的苦行道迟通达、苦行道速通达、乐行道迟通达、乐行道速通达。

Ñ(III,14): 10. In the first of the tetrads there is concentration of difficult progress and sluggish direct-knowledge. There is that of difficult progress and swift direct-knowledge. There is that of easy progress and sluggish direct-knowledge. And there is that of easy progress and swift direct-knowledge.

Sayādaw U Sīlānanda: [sluggish direct-knowledge = slow understanding]. Han: Mahāsī Sayādaw: slow special knowledge. I like Sayādaw U Sīlānanda: slow understanding.