The form of tea consumed in Japan at this time was most likely , which was the standard form in China during the Tang dynasty. The world's first monograph on tea, Lu Yu's "The Classic of Tea", was written a few decades before the time of Kūkai and Saichō. In it, Lu Yu describes the process for steaming, roasting, and compressing the tea into bricks, as well as the process of grinding the tea into powder and stirring it to a froth in hot water prior to consumption. This procedure is thought to have evolved into the method of preparing powdered matcha that later emerged in Japan.