Talk about a mystery seed.
I couldn't find a labelled photograph online to verify the identification (the seed is round and white item is a grain of rice added for scale).
Hint: it is considered to be a landscape plant.
Do you recognize what plant this seed is from? If you choose to, please leave a comment with your ideas.
Mystery Seed answers and new Mystery Seeds are posted on Tuesdays.
Edit: The answer is now posted.