@ Kiddo....there are two kind of silence. 1) verbal silence 2) Mental silence. I am guessing you did the 1st one. In the above example, it's more about mental silence. For sage like Vasistha, to be in such a state of mental silence is a spontaneous natural process. The silence which Vasistha is talking is a "natural process." What do you mean by natural process? Natural process is an effortless process where one rest in its own nature. As wise sages have declared that, when all known things come to an end what remains is pure silence. This silence shouldn't be confused with mere "maun." Maun is just a verbal silence with so many disturbances still occurring in mental level.