Let's read up on the kings of the slowbrains:

>At the start of the tournament, it was agreed that the players should make at least 20 moves within two hours. That is already very generous but ‘unfortunately, the last provision remained illusory for lack of hourglasses’, as Zukertort had to note. In the analysis of his game with Wilfried Paulsen we read at move 32: ‘White [Paulsen] reflected here for 1 hour 10 minutes, from move 22 to 34 the game lasted 7.5 hours!’ The game in its entirety lasted 12 hours, the vast majority of that time undoubtedly having been consumed by Paulsen. His brother Louis, one of the strongest players at the time, was also notorious for thinking extremely long. In the era before the introduction of the chess clock (or hourglass), he regularly drove Morphy, among others, to despair.

- Hendriks, Willy. The Ink War: Romanticism versus Modernity in Chess (p. 26)