First I also started with taking prisoners by portions.
But I can’t really understand, why can’t we just take 1000 prisoners, number them from 1 to 1000, then give a glass of wine from bottle 1 to 1st prisoner, from bottle 2 to 2nd prisoner, and so on? An only one prisoner would die in such case.
Do note that the king wants to minimize the number of prisoners involved in the experiment.
He might decide to kill every prisoner involved in the experiment if he feels that they may tell the world about his evil plans.So the king wants to minimize the number of prisoners involved in the experiment.