[On] Yom Kippur eating, drinking, washing [one's body], anointing [one's body with oil], wearing shoes, and cohabitation are prohibited.  The king and the bride may wash their faces, and a new mother may put on shoes; these are the words of R' Eliezer. But the Sages prohibit [this].

One who eats the volume of a large date —- like it and its pit —- or who drinks [the volume of] both his full cheeks is liable [for punishment]. All foods combine for the volume of a date, and all drinks combine for the volume of his cheekfuls, but food and drink do not combine.

If one ate and drank in a single period of forgetfulness, he is liable for only one sin offering.  If one ate and did work [on Yom Kippur], he is liable for two sin offerings.  If one ate foods that are not fit for consumption, or drank liquids unfit for drinking, [for example] he drank brine or salted fish fats, he is not liable [for a sin offering].

We do not afflict the children on Yom Kippur, but we train them prior to the [previous] year or prior to two years, so that they should be accustomed to commandments.