The correct contemplative practice should be done this way.

Four Foundations of Mindfulness Contemplative Practice (vipaśyanā-caryā) Diary: Currently I enter shallow meditative concentration (samādhi) fairly quickly. During sitting, I raise a "knowing," following the breath, illuminating within the mind, illuminating... Before long, with a click, the mind seems to enter the flow, instantly pure, and the brain becomes pure and bright as well. 

There is no need to deliberately deal with wandering thoughts. The physical body, feelings, and wandering thoughts are all arising-and-ceasing illusions, empty; they are not bonds. Just illuminate them, no need to counteract them—they become empty on their own. As the Heart Sutra says: “观自在菩萨，行深般若波罗蜜多时，照见五蕴皆空，度一切苦厄。舍利子，色不异空，空不异色，色即是空，空即是色，受想行识，亦复如是。” In the past I only knew how to recite it, not how to use it. Now, during training, when I put it to use, I seem to have found a bit of the feeling. The five aggregates (pañca-skandha) are not obstacles; there is no need to deal with them. Just remember that they are arising-and-ceasing illusions. Simply keep illuminating them, let them be. After illuminating for a long time, the five aggregates will become empty by themselves; the physical body and wandering thoughts will automatically become empty—this is what I currently know. 

Sitting cross-legged is merely a form. I have also tried sitting in a chair and lying in bed, raising a "knowing," illuminating within the mind, and proceeding this way—I can also enter fairly shallow meditative concentration. When sitting in meditation, full lotus, half lotus, or loose cross-legged positions all work. The key is the method of using the mind; if the method is right, one can enter. 

Assessment: When the mind is not calm, there are many objects of attention within, but we have a goal—contemplative practice (vipaśyanā-caryā) on the breath is the primary goal, one might even say the only task. Grasping the main matter and the great matter is the only way to complete the task with both quality and quantity assured. Do not chase after thoughts other than the breath; those are unimportant. Thoughts come and go and never stay; even if you try to keep them, they cannot be kept. Just do the proper work without distraction. 

The mind attends only to the breath, like lamplight shining only on the breath; all the surrounding bodily sensations and stray thoughts are no longer in the mind—they disappear, become empty. And on the breath, one will discover phenomena that could not be discovered before, that is, the truth and facts. As for what those truths and facts are, each person experiences them for themselves in the course of doing the work; what each person discovers may differ somewhat, but the final result is the same despite different paths: realizing the emptiness of the five aggregates (pañca-skandha) and non-self.

In contemplative practice (vipaśyanā-caryā), the specific posture does not matter; one must practice whether walking, sitting, or lying down, combining movement and stillness so they complement each other. But sitting cross-legged has its advantages: it promotes smoother circulation of qi and blood, greater harmony of the physical body, a calmer mind, and more concentrated thought. Afterwards, combining it with walking and physical activity allows the circulation of qi and blood to be fully regulated and to flow throughout, which is more beneficial to the body, and the mind will be purer.