Make sure you have some air space space under the glass. Otherwise moisture can creep in via capillary action and damage the finish & wood. Also it keeps the finish and glass from "blocking."

Do not use the clear plastic pads. The plasticizer in these can turn the finish soft and gooey, essentially eating it away. I always recommend the felt stick-on pads. Not quite as nice looking, but will not damage the finish.

We put glass on our kitchen butcher block table back in the late 80s.
Right on the wood.

NO problems with that at all. The butcher block looks as good as the day we bought the table.

I use coasters and trivets to protect my antique table from heat and wet glasses. Works well, looks lovely and there is no worry about glass damaging the table top. I have also seen wood bleached by sun shining through the glass.

I agree with Lindac I thinks it's best not to use glass the coasters look good and the glass can cause other issues such as moisture build up.

I suppose in as much as it is an antique table and the wood is well dried there would not be much of an issue with moisture retained in the wood only with room humidity so you could probably go either way with or without a glass top. The table would look better with the wood top but with the glass top you would have less to worry about.