Letter bomb

A letter bomb is a type of Muggle explosive device that can be placed with in correspondence sent by Muggle Mail. If properly wired, the device will detonate upon the opening of the letter.

In 1991, after Harry Potter hesitated in bringing Vernon Dursley the mail, which included his first Hogwarts acceptance letter, Vernon joked that Harry might be "checking for letter bombs" and then chuckled at his own joke.

Appearances

 * Harry Potter and the Philosopher's Stone