妙法蓮華經玄義 4.20

4.20

八勝處者，初兩勝處位在初禪；三、四兩勝處位在二禪；後四勝處位在四禪。三禪樂多心鈍，故不立也。前背捨，緣中多少不得自在，是故勝處更深細觀察少多好醜，悉使勝知勝見，如快馬能破陣，亦能自制其馬（云云）。

As for the eight spheres of mastery: the position of the first two spheres of mastery is in the first dhyāna; the position of the third and fourth spheres of mastery is in the second dhyāna; the position of the latter four spheres of mastery is in the fourth dhyāna. Because the third dhyāna has much bliss and the mind is dull, none are established there. In the preceding liberations, one does not attain sovereignty over whether the objects are few or many; therefore, in the spheres of mastery, one contemplates more deeply and minutely few, many, fine, and ugly, causing all to become mastered knowledge and mastered vision—just like a swift horse that can break an enemy battle line and can also be restrained by its rider (and so forth).