How would you read the volume of the liquids such as mercury whose meniscus curves upward at the center?

Answer 1

Measure at the top of a convex meniscus. But as you can see from the diagrams in the reference, use a graduated cylinder designed to be accurate for whatever you are measuring.

Answer 2

same with liquids whose curve downward, you should measure the middle of the curve, in case of mercury and alikes, is the highest point, the TOP of the curve!

hope it help