《荀子·大略》
对方站着时，在他前面六尺处注视他，而最远是六六三十六尺，即在三丈六尺之处注视他。
立视前六尺而大之－－六六三十六，三丈六尺。
If the person is standing, you should look at him at a distance of six feet, but under no circumstances should your gaze exceed three zhang and six feet, or thirty six feet.