Koans are used to interrupt the logical thought pattern. There are hundreds of them available. Sokuzan discusses on the reflection of them.
Sokuzan has an open interview with Sangha members that choose to do so.
Sokuzan’s talk comes from Atisha’s Seven Points of Mind Training. Point Three: Transforming Bad Circumstances into the Way of Enlightenment.
Mountains and rivers (Sansuikyo in Japanese) was written by Dogen in the 13th century and can be found in the Shobogenzo. Sokuzan discusses this and his process.