​Poisonous plants that can kill a person within minutes/an hour?

Hay everyone, im too scared to ask goggle this so imma put it here. I’m writing a short story where someone poissons another person’s drink.

For this story I need a poison that is natural (like a flower), fast acting, can be hidden in a drink (even if it would give the drink a bad taste), and that would have some external symptoms (shortness of breath, clamminess, dilated pupils, sweating, eta). It doesn’t have to be one that’s easy to get but that would be great if that exists.

Thank you in advance!