I agree that this is most likely a seed, given its roughened outer coat and 2 internal structures which may represent seed leaves or "cotyledons."
On higher magnification, you can see the characteristic rigid, geometrically shaped cells that are also characteristic of plant material:
The differential diagnosis could include the small intestinal flukes such as Heterophyes heterophyes, given it's similar size and shape. However, the internal morphology is much different, and the presence of diagnostic eggs in the uterus easily allows for the diagnosis.
Shown above is an adult H. heterophyes fluke.
And now an 'inspirational' poem from Blaine Mathison:
Going to the hospital one man felt the need
when going to the bathroom he started to bleed
amoeba? Not a chance!
Shigella? Take another glance.
Why it’s merely the remnants of a seed.