The tocha of Japan was likely directly inspired by the doucha 斗茶 custom of Song China — except the rules and game were completely different in Japan. In Song China, the aim was to produce the whitest froth, the longest lasting froth, and finally and most skillfully, conjure pictures in froth (much similar to latte art). Unfortunately, the latter skill died out and has been difficult to reproduce.
In today’s China, doucha now means to compare and rank various samples of a specific tea either professionally between tea producers or tea companies, or informally between tea friends.