Classical Chinese had a much larger phonemic inventory than modern Mandarin, and notably no tones. Below are a collection of Classical Chinese reconstructions in IPA that are all pronounced yì in Mandarin today. (like "ee" for English speakers). The creation of tones and other sound changes were fairly predictable, so as you say, the hints often still help today.

- ŋjajs 議; 'discuss' - ŋjət 仡; 'powerful' - ʔjup 邑; 'city' - ʔjək 億; '100 million' - ʔjəks 意; 'thought' - ʔjek 益; 'increase' - ʔjik 抑; 'press down' - jak 弈; 'Go' - ljit 逸; 'flee' - ljək 翼; 'wing' - ljek 易; 'change' - ljeks 易; 'easy' - slek 蜴; 'lizard'