Yosef Karo, Translation:Shulchan Aruch — Orach Chaim 611…
“ If there is a fire on Yom Kippur, it is permitted to save one meal for the evening just as one saves the afternoon meal on Shabbat (Ra"n chapter "Kol Kitvei") . It was already explained in 334 how to behave nowadays with respect to a fire on Shabbat, and the same applies to Yom Kippur. It is the practice for children to play with nuts (Agudah and Mahari"l) and we should not stop them, even before Mincha. ”
