Speaking on Thursday in the room where he later died, Mr Goodall said: "My life has been rather poor for the previous year or so".
Goodall did not have a terminal illness but said his quality of life had deteriorated and that he wanted to die.
On his final day, before he went to a Swiss clinic to die, David Goodall spoke about his 104 years of life - and his scheduled death.
Goodall was an honorary research associate at Perth's Edith Cowan University, and had produced dozens of research works.
"I would love to be able to walk into the bush again, and see what is all around me", added the father of four, who during his long life had three wives.
He stressed that it was his "own choice to end my life" and said: "I look forward to that".
"My entire life was out in the area (doing work), however that I cannot move from the industry now", said Goodall, who needs a wheel chair and also walking frame to go about, during a meeting in his Basel hotel.
In Switzerland, assisted suicide is allowed only if the person assisting acts unselfishly.
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Only a handful of countries have legalized assisted suicide or euthanasia, including Belgium, Luxembourg, and the Netherlands.
Derek Humphry, founder of the Hemlock Society (now two organizations - Compassion and Choices, and Final Exit Network), wrote in 2000 about the "unspoken argument" for assisted suicide - that it would be cheaper to let the elderly and disabled die than to keep them alive. Now seven states (and Washington, D.C.) have laws allowing assisted suicide for terminally ill, mentally competent adults - Hawaii, Oregon, Vermont, Montana, Washington, Colorado and California.
Goodall had attempted but failed to commit suicide on his own earlier this year.
Victoria last year became the first State to introduce a euthanasia Bill, effective in June next year, allowing terminally ill patients to end their lives.
"I am awaiting this", he said of his impending departure. He said: "I'll be thinking about the needle and hoping they aim right!".
Moritz Gall, a lawyer with assisted-suicide advocacy group Life Circle, stressed to reporters that the centenarian had the option of changing his mind up until the last minute.
"The process of dying can be rather unpleasant, but it need not be", he said.
"The message I would like to send is: once one passes the age of 50 or 60, one should be free to decide for oneself whether one wants to go on living or not", he said, the Swiss News Agency, SDA-ATS reported.