Adventurous cooks might consider one of the recipes in Peter Ross's new book, but the author of the tome on unusual historical cuisine says it's probably best not to try a dish featuring animals like swans, peacocks or porpoises.

"You could cook a meal, but it could be quite a strange meal," said Ross, the chief librarian at Guildhall Library in London and the author of The Curious Cookbook, which looks at a wild range of cookery from medieval times right through to the Second World War.

"It's mostly the medieval recipes where you're going to have a problem — because they were eating things like swans, peacocks, porpoises."

The new book also features a live frog pie that dates from the 17th century.

Ross said the dish containing live frogs was "basically an entertainment" that was served during a high-class meal.

"You would have your servant bring in a pie, and unbeknownst to all your guests, it was just a pie crust on top of a dish," the author said from London. "So when you invited one of your guests to cut into it, the frogs would jump out of the pie."

The pie was essentially used as an ice-breaker and to amuse people — not to eat.

Curious readers can also learn more about barbecued otter, poisoned purple pear, stewed sparrows, viper soup and imitation entrails. The latter, Ross said, is "quite a complicated dish" from medieval times that involves threading dried fruit and nuts onto a string, winding it around a spit, cooking it in front of an open fire and covering it with batter as it heats up.

The result "looks a bit like entrails," Ross said. The cook would take it off the spike, spread it on the plate and surprise the guests with a dish featuring fruit and nuts.

"What I wanted to show in my book was that although these things might seem extraordinary to us, they also demonstrate how sophisticated our ancestors were."