瑜伽論記 8.91

8.91

或以其身於諸牆壁直過無礙乃至履上如地者，此由空界想成，或如飛鳥等，此由輕舉柔軟想成。

"Or passing straight through walls and fences with one's body without obstruction, up to treading upon [water] as if on ground": this is accomplished through the perception of the element of space. "Or like a flying bird, and so forth": this is accomplished through the perception of lightness and pliancy.