Guess what? Or rather, guess what seeds are these from? Interestingly, while I planted numerous plants of this particular species, I have never check out the seeds before this. Until recently, when I broke open the black pods, that gave out the rattling sound when shaken, to sow the seeds, I have no idea how the seeds look like.
In fact, these seeds look just like small hearts, and I mean the real asymmetrical ones and not the fake hearts. They are just lovely, aren't they?
Oops, I almost forgot to mention these are the seeds of the Crotalaria retusa (Family: Fabaceae / Leguminosae), which is commonly known as Rattlebox or Rattleweed because the sound produced by rustling the pods reminds one of the Rattlesnake.