The book is "Calculus Made Easy" by Silvanus P. Thompson. I had a copy of this some years ago. He skips delta epsilon proofs entirely and uses the infinitismal

The book is "Calculus Made Easy" by Silvanus P. Thompson. I had a copy of this some years ago. He skips delta epsilon proofs entirely and uses the infinitismal method to describe derivatives and integration. Makes for a very slim volume.