One day Yao-shan Wei-yen (750-834), one of the well-known Chinese Ch'an master, was asked by the host of the monastery to give his sermon to the assembly who for a long while was expecting his teaching. Yao-shan said: "Strike the bell."
ZAZEN MEDITATION GUIDE - Chapter 5. Garments for Sitting
Garments for Sitting You will not be comfortable with any kind of tight, heavy or hard fabric clothing when you sit in zazen. Therefore, any loose fitting garment made of fine, soft fabrics will be better in sitting. When you do zazen, wearing garment is much better than wearing nothing.