daf bit: Sanhedrin 45
Previously this tractate described the extra care taken in capital cases, lest someone be wrongly condemned. If someone is found guilty, then right up to the point of execution they continue to look for reasons to acquit him.
The mishna then discusses how stoning (one of four types of execution) is carried out. The two witnesses whose testimony led to the guilty verdict go first -- the witnesses themselves must participate in the execution. The court, witnesses, and observers take the condemned to a place that is twice a man's height. One witness pushes him off so that he lands on his heart. They then turn him onto his back to see if the fall killed him. If not, the other witness takes a (prepared, heavy) stone and drops it on his chest. If that doesn't kill him, then all Israel -- meaning all those assembled -- stone him. (45a)
The g'mara does not discuss how this group stoning is conducted, but it is unlikely to resemble the "angry mob" sometimes depicted in media.
Twice a man's height is not that long a fall. (I wonder how often the push alone was fatal.) I don't know what factors led to this height being the practice and not something a little higher. (Presumably they don't want to go too high out of dignity for the body; they want to execute him, not splatter him.)
Today's daf is 46.