瑜伽論記 9.91

9.91

言如是境界至所知邊際等者，此真如理，對苦空等，為最第一，無有上故稱無上。若見此理，證究竟名所知邊際，齊此已外，一切智人正勤思釋，更無去處，皆悉退還不能越度。

Regarding the statement "Such an objective sphere" down to "the boundary of the knowable": This principle of tathatā, contrasted with suffering, emptiness, and the like, is the most supreme; having nothing above it, it is called unsurpassable. If one sees this principle, realizing the ultimate is called the boundary of the knowable; beyond this limit, though all-knowing persons diligently contemplate and interpret, there is no further place to go—they all turn back, unable to exceed it.