Alhumdulilah forever!   This is so indescribably sweet.

 

"And We send down from the sky blessed water whereby We give growth unto gardens and the grain of crops,"   (50:9) Most Noble Quran.



This image: A park walkway empty in the rain


Salam kiddos.   Just imagine what life would be without rain?   We would have no food and no potable water to begin with.  Forget every other luxury. 

And you know what?  If your house has a yard with grass and flowers, try collecting rainwater in summer and storing it in barrels or water containers.  Use this pure water to nourish your yard.  This will also help reduce runoff pollution.  When rain water flows on the ground, it picks up contaminants from the soil and spreads them in portions of the landscape.  

I think the likelihood of mercury is presumably more because of the Ommayad ruler's well-known contacts with the Byzantine ruler.  Nonetheless arsenic is also a possibility.

You're right, arsenic was very commonly used as a murder weapon in Europe in early and mid 2nd millennium.  Actually during European Renaissance, methods of poisoning were studied and learned like art or science. 

The poisoner's job was viewed as that of any other professional.  He took appointments from clients who wanted someone fatally poisoned.  The client would name the victim and then a contract would be made, the poisoner would then set the price and would be paid when the job was done.  Women married to wealthy men suddenly becoming wealthy widows were common incidents.
Poisoner's job was a family trait in medieval Europe, often with "high profile" criminal clients.  One of such clients who sought the poisoners' help to administer arsenic to several of his opponents was a pope in the 1400s - Pope Alexander VI - a notorious womanizer who had several mistresses and illegitimate children.

It was from the late 1700s when this sick profession gradually disappeared after methods of postmortem detection were discovered, particularly considering that there was capital punishment for murder in Europe back then.

Good idea.

Welcome and thanks Sis