首楞嚴義疏注經 4.445

4.445

「而此界性設雖十方，定位可明。世間只目東西南北，上下無位，中無定方。」

"Although the nature of these boundaries is assumed to have ten directions, their determined positions can be clearly known: in the world, one identifies only east, west, south, and north; above and below have no fixed position, and the center has no fixed direction."