| Clue | Source | Date |
|---|---|---|
| Biological measure of expended energy | The Telegraph Cross Atlantic | 14 Jun 2025 |
| Biological number | Thomas Joseph | 06 Sep 2019 |
| Measure of energy expended | Wall Street Journal | 26 Dec 2018 |
| Measure of energy expended | ||
| Burning figure | New York Times | 15 Dec 2017 |
| Burning figure |