Lucrezia Borgia invited a prospective victim to lunch. They ate a hearty meal of roast venison, with a selection of fresh vegetables, all washed down with the finest wine imported from Bordeaux, France.

After the meal, they ate figs and freshly picked grapes.

“Just one apple left”, said Lucrezia, “I insist you have it.

“No”, said the guest, “I couldn’t”.

“Tell you what”, said Lucrezia, “we’ll share it”, and promptly sliced the apple in two with her sharpest knife. The guest and Lucrezia started to eat their respective halves when the guest’s eyes rolled towards the ceiling and he fell over, dead.

“Another victim successfully dispatched,” thought Lucrezia.

How did she do it?