NEW HAVEN, Conn.--Several cookbooks tucked away in the depths of a Yale University library contain what may be the world's most time-tested recipes.

The recipe collections--inscribed on three Mesopotamian clay slabs dating to 1700 B.C.--are probably the oldest cookbooks in existence, according to William W. Hallo, curator of the Yale Babylonian Collection.

The cuneiform figures scratched into the tablets provide instructions for dozens of Mesopotamian stews, vegetable dishes and meat pies.

The recipes reveal "a cuisine of striking richness, refinement, sophistication and artistry," said Jean Bottero, a French assyriologist.

"Previously we would not have dared to think a cuisine 4000 years old was so advanced," Bottero wrote in the March 1985 issue of Biblical Archaeologist magazine.

Twenty-one recipes for meat and four for vegetables are written on the best preserved of the tablets. Instructions call for most of the food to be prepared with water and fats, and to simmer slowly in covered pots, Bottero said.

The tablets most likely date back to the Old Babylonian period of Mesopotamia, Bottero said. The area between the lower Tigris and Euphrates rivers in what is now Iraq is often referred to as the cradle of civilization.

"They are recipes and as such practically a unique genre that one simply has not encountered before in cuneiform literature," said Hallo, a professor of Assyriology and Babylonian literature at Yale.

Yale recently celebrated the 75th anniversary of its Babylonian collection, which contains about 40,000 items.

Meats included stag, gazelle, kid, lamb, mutton, squab and a bird called tarru. Frequently mentioned seasonings included onions, garlic and leeks, while stews were often thickened with grains, milk, beer or animal blood. Salt was sometimes mentioned.

Scholars have not been able to identify all the ingredients, including tarru and two seasonings called samidu and suhutinnu.

"What is striking about all this is the multiplicity of condiments that were added to one and the same dish and the care with which they were combined into a blend of often complimentary flavors," Bottero wrote in the 1987 edition of the Journal of the American Oriental Society.

"These combinations obviously presume a demanding and refined palate--even when far removed from ours--betraying an authentic preoccupation with the gastronomic arts."

The Mesopotamians "adored their food soaked in fats and oils," Bottero wrote. "They seem obsessed with every member of the onion family, and in contrast to our tastes, salt played a rather minor role in their diet."

Many Babylonians "subsisted on the barest necessities" and probably did not eat the food described in the tablets, Hallo said.