Among them, drilling is a metaphor, which will be mentioned later. The advantage is that people have a more practical understanding of the word "drill", which shows his rigorous and diligent learning attitude and selfless and fearless spirit of struggle.
The phrase that he digs into ancient books like searching for treasure in the earth's crust comes from Mr. Wen Yiduo's article, from which we can see Mr. Wen Yiduo's scholar style of perseverance, assiduous study and exhaustion.