1,249. They Used to Light Signal Fires

Hilchos Kiddush HaChodesh 3:7

When the court declared a month full because witnesses did not arrive on the 30th day, they would retire to a particular spot for a feast on the 31st day, which was Rosh Chodesh. They would not go there on the night of the 31st day; they would go at daybreak, before sunrise. No fewer than ten men would go to attend this banquet, which would include bread made from grain and pulse. This is what is meant when sources refer to the feast of the full month.

Hilchos Kiddush HaChodesh 3:8

Originally, when the court sanctified the new month, they would light signal fires on mountaintops in order to notify people who lived far away. When the Samaritans began rebelling against the religious authorities, they would light fires at inappropriate times in order to confuse things. The court then discontinued the fires and started sending messengers to notify the people. These messengers were not empowered to violate holidays, Yom Kippur or Shabbos. Only declaring the new month superseded Shabbos, not observing it.