I have heard of sages being able to kill themselves with meditation. How do they do this?
Many yogis have claimed to be able to do this - the scientific evidence is not convincing.
In a controlled study, it was found this was not based on meditative control, but on holding the breath and considerable tensing of the muscles in the abdomen and thorax. This resulted in reduced blood flow, but did not stop the heart. One subject was able to slow his heart for a maximum of 3 seconds using this method.
Theravada Buddhist Answer.
Samatha meditation is designed to focus the mind, to cultivate the Jhana states, thereby preparing the mind for the insight-portion of the Buddha's path.
Vipassana meditation is designed to allow the mind to cultivate a deep and liberating understanding of conditioned reality. Vipassana meditation is the only meditation type that can completely eradicate the 3 layered defilements, ie. the deepest layer of latent tendencies (anusaya).
With that in mind, meditation cannot kill you but it can "kill" (cut off the latent tendencies at the root) the three root defilements.