Ideal money is a security that has no dimension.
Ideal money is atomic, structureless, has no extension but has infinite duration.
Ideal money has zero volatility and lasts forever. It has an infinite uninteresting future and an episodically interesting present characterized by sudden changes in ownership.
Ideal money is the security whose transaction is also the settlement.
Whoever finds ideal money can keep it and becomes the new owner. Whoever loses it has no claim on it.
Giving money a spatial dimensional (a coin, a note) implies a less than infinite duration and converts it from ideal to real and approximate.
Money in practice is the smallest security with the longest duration.
The possibility of time variation destroys its ideal quality. A bond, perishable with finite duration, cannot be money.
Whats bad about usury and even interest is the imposition of time on money.
(Ideal money has zero extension and infinite duration. What security, conversely, has infinite extension but zero duration? An ideal bubble?)