Final answer:
Jan Baptista van Helmont would have taken measurements of soil and plant weight to carry out his experiment on plant growth, which led to early insights into photosynthesis.
Step-by-step explanation:
The student has asked what measurements Jan Baptista van Helmont would have taken. Van Helmont was a Flemish chemist, physiologist, and physician who lived during the late 16th and early 17th centuries. He is most famous for his experiment in which he aimed to find out whether plants grew by taking material out of the soil. Van Helmont planted a willow tree in a pot with a known amount of soil and weighed the soil. He then watered the plant with rainwater but did not add anything else to the pot. After five years, he found that the plant had increased significantly in weight, but the soil weight had barely changed. This experiment was one of the first to suggest that plant growth did not come solely from soil but also involved intake from water and air, introducing the idea of gases playing a role in plant nutrition and leading to the discovery of photosynthesis.