Not an image that I had heard before, but the ideas behind it are quite useful:
The practice of “remaining like a log ” is based on refraining, not repressing. When you realize you’re thinking, just acknowledge that. Then turn your attention to your breath flowing in and out, to your body, to the immediacy of your experience. Doing this allows you to be present and alert, and thoughts have a chance to calm down.
With this practice, it can be helpful to gently breathe in and out with the restlessness of the energy. This is a major support for learning to stay present. Basic wakefulness is right here, if we can just relax. Our situation is fundamentally fluid, unbiased, and free, and we can tune into this at any time. When we practice “remaining like a log, ” we allow for this opportunity.
Pema Chodron, No Time to Lose: A Timely Guide to the Way of the Bodhisattva