Much cooking was probably done out of doors, and took the form of grilling, roasting, frying, or boiling over a fire, or baking in hot ashes; the clay oven was perhaps reserved for bread. Cooks depicted in Athenian comedy of the 4th century BC happily list the methods they preferred for preparing various dishes (and, in particular, various kinds of fish). Although all too brief for the non-initiate, these laconic instructions are consistent enough with one another to carry some conviction: there clearly was a body of knowledge that professionals and household cooks learnt and transmitted by word of mouth and by example. At least one cookery book, by Mithaecus, had been written (there were others later) but only a few scraps survive. Also in the 4th century Archestratus of Syracuse had written a humorous gastronomic poem, evidence that the expertise of cooks could be acquired by interested laymen and that travel and trade was encouraging the appreciation of local produce and regional cuisine.