Measuring wheel and oil lamp: what they have in common

1. Step 1. Measuring wheel — is part of — Planimeter. A counting wheel integrates the area.
2. Step 2. Planimeter — has part — Wheel. A measuring wheel computes the area.
3. Step 3. Wheel — has part — Axle. A wheel turns on an axle.
4. Step 4. Axle — is part of — Yo-yo. The axis between the discs.
5. Step 5. Yo-yo — is made of — Clay. Greek yo-yos were terracotta.
6. Step 6. Clay — is material for — Oil lamp. Later — clay ones.

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