Sushi actually began as a way of preserving fish. The raw, cleaned fish was pressed between rice and salt by a heavy stone for a few weeks. After a few weeks, the stone was removed and replaced with a light cover. A few months after that, the fermented fish and rice were considered ready to eat. Not until the 18th century did a chef named Yohei decide to serve sushi in its present form and forget about the fermentation process altogether. The use of vinegar rice, however, probably dates back to the fermented taste of early sushi. In Osaka there is still an elaborate tradition of sushi pressed with rice in wooden boxes. This type of sushi is called hako-zushi. The sushi most commonly known among Westerners comes from Edo, the old name for Tokyo, and consists of hand-rolled sushi specifically called nigiri sushi. Sashimi is fresh, raw, chilled, sliced, and elegantly arranged. Ideally, sashimi is best when fresh, but most fish freeze well and are served after thawing. Sashimi may be garnished with raw vegetables, leaves of knot grass, parsley, lettuce, shredded daikon, and sometimes seaweed or cucumber. Sashimi is odorless and very delicate. When sliced thick it is served with soy sauce, when sliced thin served with ponzu, a citrus flavored sauce. Wasabi, red pepper, and green onions may be served to mix with sauces as well. Maki sushi contains strips of fish or vegetables rolled in rice and wrapped in crisp, thin sheets of dried seaweed. There are many combinations that even the most timid can enjoy such as smoked salmon, fresh crab, or shrimp. The adventurous can sample delicacies like octopus, raw clams, sea urchin, or salted fish roe. Nigiri sushi is a slice of fish (cooked or uncooked) pressed by hand onto a pad of rice. Fish roe is also served as nigiri sushi in a style called gunkan, meaning "boat." Nigiri sushi contains a hint of horseradish and is meant to be dipped in soy sauce. They are always served in pairs.