Actually he did not say anything which makes sense

Weight is the effect of.... nowadays we know that

If you asked the question : what is matter ?
before Newton,people would answer , something like :

Its weight inside a volume

Weight was supposed to be a synonimous with matter , the weight of a body being , apparentely, a constant on the surface of the earth
All other properties shape, color, hardness etc can change but weight can not
Consequently weight was not supposed to be a property of matter rather the matter itself
For the same reason after Newton but before Einstein mass became a syonimous with matter even though , strictly speaking, it should be only a property of matter namely its Inertia

Einstein discovered that even the mass of a body is variable , consequently you should drop the equivalence

matter == mass

Same as you did with

matter = weight

The logical conclusion is that equation does not entail matter annhilation
Apparentely ;

you could lose mass without losing matter

Is above claim correct ?



The point is that even scientists speak of matter annihilation