Further, such continuity of thought is Dhyana or meditation. It can come only when the limbs are not active and the mind is calm. Concentration being an uninterrupted and unintermittent current of thought sent towards a particular object, the sitting posture becomes indispensable. The word Upasana also denotes exactly what meditation means, that is concentrating on a single object with a fixed look, and without any movement of the limbs. This is possible only in a sitting posture.
Meditation denotes a lengthened carrying of the same train of ideas.
We ascribe thoughtfulness to those whose mind is concentrated on one and the same object while their look is fixed and their limbs do not move. We say that Sri Ramakrishna is thoughtful. Now such thoughtfulness is easy for those who sit. The wife sits and thinks deeply over her husband gone in a distant journey. Dhyana or meditation is thinking on one subject continuously, without the inrush of ideas incongruous with the subject of thought.