From the article:
LAUDIA Severa wasn't to know when she invited her friend Sulpicia Lepidina to her birthday party that the brief note she sent would end up as one of the most treasured handwritten documents in history.
The friends were wives of fort commanders on the Roman Empire's northwestern frontier in Britain about 1900 years ago. The note, written in ink and Latin script on a slither of birch or alder, asked Sulpicia to be there "to make my day more enjoyable".
The thin wooden tablet, along with hundreds of others detailing daily life at the garrison of Vindolanda, in present-day Northumberland, found its way on to a rubbish heap and may have been earmarked for burning.