A dream of odd coffee

Dream:
In a coffeehouse in a free-standing old stone building in central Copenhagen (as usual bearing no resemblance at all to the Copenhagen I'm used to). Colored painted walls and hardwood floors.

I had a cup of coffee, probably café au lait, which somehow was made in relation to the philosophy of an old dead philosopher. Who was also there.

The coffee had the odd property that while I drank it, and only while actually sipping it, all curved lines in my sight turned to straight lines. Circles, like the top of the cup, turned to octagons...

I did it many times. It was most extraordinary, and I have no idea what it means, if anything!