In ancient times loyal officials were often threatened with the harshest tortures.
Tips
history
From the 《汉书·刑法志》: 大刑用甲兵,其次用斧钺,中刑用刀锯 — knife and saw were 'middle-grade' punishments (mutilation), while 鼎镬 (boiling cauldrons) belonged to capital execution. The four together form a complete catalog of imperial torture.
memory
Read it as a tool kit: 刀 (knife), 锯 (saw), 鼎 (tripod cauldron), 镬 (large cauldron) — two for cutting, two for boiling. The grimmest mnemonic, but it sticks.