Somehow, if you could manufacture a really smooth frictionless surface, that if you took a hockey puck or something and an air cushion and you give it a push, in some idealized world, it'll travel forever.

如果你制造一个绝对光滑无摩擦的表面,然后在上面放个冰球或者别的什么,或者气垫,然后推它一下,在理想条件下,它会永远运动下去

耶鲁公开课 - 基础物理课程节选

First I go over the physical posture you should have because when you're sitting like we usually sit on the round cushion or the floor, re free of contact with people usually both your knees and your butt are for the kneeling.

首先理顺应有的身体姿势,因为打坐时,像我们常会坐在圆坐垫,或地板上，你要确定自己身旁不要有人，you，make，sure，you‘,通常两膝和臀部都要注意,都要碰到地面。

普林斯顿公开课 - 人性课程节选